Personal warming systems and apparatuses for use in hospitals and other settings, and associated methods of manufacture and use

ABSTRACT

Personal warming systems and apparatuses for use in hospitals and other settings are disclosed herein. In one embodiment, a heating pad for warming a patient during a hospital procedure can include a heating element and a patient support portion. The heating element can include one or more radiolucent, or at least generally radiolucent, features. The radiolucent features can include conductive paths supported by a flexible substrate. The conductive paths can include conductive yarns oriented in linear and/or non-linear patterns on the flexible substrate. In one aspect of this embodiment, the conductive yarns can include conductive strands having a metallic plating, such as silver plating.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of pending U.S. patent applicationSer. No. 10/657,727, filed Sep. 8, 2003, which is a Continuation-In-Partof pending U.S. patent application Ser. No. 10/419,705, filed Apr. 19,2003, which claims the benefit of U.S. Provisional Patent ApplicationNo. 60/457,528, filed Mar. 24, 2003, and claims the benefit of U.S.Provisional Patent Application No. 60/374,853, filed Apr. 20, 2002, andwhich is a Continuation-In-Part of pending U.S. patent application Ser.No. 09/880,725, filed Jun. 12, 2001, now U.S. Pat. No. 6,653,607, whichclaims the benefit of U.S. Provisional Patent Application No.60/212,380, filed Jun. 14, 2000. Each of the above-identified patentapplications is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The following disclosure relates generally to personal warming systemsand apparatuses and, more particularly, to personal warming systems andapparatuses for warming patients undergoing various hospital procedures.

BACKGROUND

Maintaining patient body temperature at an acceptable level can be veryimportant during some medical procedures because of the significanteffect it can have on the outcome of the procedures. If a patient's bodytemperature is allowed to drop below an acceptable level, the patientcould develop hypothermia which can prolong or complicate recovery. If apatient can be kept warm before, during, and after surgery, for example,then post-operative problems such as excessive bleeding, infection,shivering, and cardiac distress can be minimized. Maintaining thepatient's body temperature in a surgical setting, however, may bedifficult for a number of different reasons. One reason is that theoperating room is typically air-conditioned at a relatively cooltemperature to maintain air cleanliness and to provide the medicalpractitioners with a comfortable working environment. Another reason isthat many surgical procedures require that at least a portion of thepatient be exposed for surgical access. Such surgical access can furtheraccelerate patient cooling if it opens up a large portion of thepatient's body, such as the chest cavity. In addition, the onset ofhypothermia during certain medical procedures may be accelerated by thepatient's body position. For example, elevating the patient's leg toharvest veins for heart surgery may accelerate a decline in thepatient's body temperature.

Cardiac catheterization is an invasive procedure in which the doctorthreads a catheter through an artery in the patient's arm, groin, neckor leg to the patient's heart. A special dye is introduced into thecatheter that allows the doctor to view arterial blockages with an x-raymachine to diagnose the patient's condition. The procedure oftenrequires that a substantial portion of the patient's body be accessibleto the doctor for comprehensive x-ray imaging to examine the variousblood flows. As a result, much of the patient is exposed or only lightlycovered during the procedure, which may cause the patient's bodytemperature to drop to undesirable levels. For this reason, it may bedesirable to warm the patient during the cardiac catheterizationprocedure to prevent the onset of hypothermia.

Various devices exist for warming patients undergoing medicalprocedures. One such device pre-warms blankets placed over the patient.Another such device circulates heated air through a sealed blanketplaced over the patient. Yet another such device circulates heated waterthrough a sealed blanket placed over the patient.

There are a number of shortcomings associated with existing patientwarming devices. The use of pre-warmed blankets, for example, can beexpensive because the blankets are often disposed of after each use.Devices utilizing heated air have the additional drawback of circulatinghigh temperature air in close proximity to patients who are oftenanesthetized. If a hot air duct associated with such a deviceinadvertently contacted an anesthetized patient, the patient couldsustain serious burns before the practitioner or operator noticed theoversight and corrected the situation. In addition, all of theseexisting patient warming devices generally require high energy inputs toachieve the desired temperatures.

Another shortcoming often associated with existing patient warmingdevices is that most are configured to inefficiently warm the patientfrom the top down. This shortcoming often limits use of such devices tothose portions of the patient where the medical practitioner does notrequire access. For example, if the patient is undergoing open heartsurgery, then use of such devices would be precluded near the patient'schest. Unfortunately, however, in many surgical procedures the areawhere the practitioner is operating is often the area most in need ofadditional warmth.

A further shortcoming often associated with existing patient warmingdevices is a lack of adequate cleanliness. Body fluids, for example, canoften get inside various parts of conventional patient warming deviceswhen such devices are used in a surgical setting. These fluids canpresent cleanliness concerns for subsequent use of the device. This isone reason why many conventional patient warming devices incorporatedisposable components. The use of disposable components, however, canincrease the costs of surgical procedures.

Yet another shortcoming often associated with existing patient warmingdevices is an inability to adequately control the rate or level ofpatient warming. In certain circumstances, uncontrolled patient warmingmay complicate the surgical procedure or cause negative side effects inthe patient.

Various products exist for monitoring patient egress from hospital beds.U.S. Pat. Nos. 6,307,168; 6,297,738; 6,025,782; and 5,623,760 to PaulNewham may disclose various aspects of such products. One such productincludes a sensor coupled to a mattress that transmits a signal to anurse's station when a patient moves off of the mattress and exits hisor her bed. The mattress encloses a polyester fabric that supports twobands of conductive strands. The conductive strands can include silverplated nylon strands, such as those provided by Noble Fiber Technologiesof 421 South State Street, Clarks Summit, Pa. 18411, that are woven intothe fabric in a linear array. The two bands of conductive bands areelectrically coupled to the sensor. When a person moves off of themattress, the sensor detects a change in the capacitance between thebands and a signal is sent to the nurse's station indicating that thepatient has exited the bed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top isometric view of a patient warming system configured inaccordance with an embodiment of the invention.

FIG. 2 is a side elevational view of a control unit of the patientwarming system of FIG. 1, configured in accordance with an embodiment ofthe invention.

FIG. 3 is a top view of a user interface of the control unit of FIG. 2,configured in accordance with an embodiment of the invention.

FIG. 4 is a partially hidden top isometric view of a heating padconfigured in accordance with an embodiment of the invention.

FIG. 5 is a partial cross-sectional side elevation view of the heatingpad of FIG. 4, configured in accordance with an embodiment of theinvention.

FIG. 6 is a foreshortened cross-sectional side elevation view of theheating pad of FIG. 4, configured in accordance with an embodiment ofthe invention.

FIG. 7 is a schematic diagram of the control unit and the heating pad ofFIG. 1, configured in accordance with an embodiment of the invention.

FIG. 8 is a schematic diagram of a control unit and a heating padconfigured in accordance with another embodiment of the invention.

FIG. 9 is an enlarged partial cut-away isometric view of a portion ofthe control unit of FIG. 1 illustrating a connector shield configured inaccordance with an embodiment of the invention.

FIG. 10 is a top isometric view of a patient warming system configuredin accordance with another embodiment of the invention.

FIG. 11A is an enlarged front view of an accessory control unitconfigured in accordance with an embodiment of the invention.

FIG. 11B is an enlarged front view of an accessory control unitconfigured in accordance with another embodiment of the invention.

FIG. 12 is an exploded, partially hidden, partially cut away topisometric view of a heating pad configured in accordance with anotherembodiment of the invention.

FIG. 13 is a partially cut away, top isometric view of a heating padconfigured in accordance with another embodiment of the invention.

FIG. 14 is a partially schematic enlarged top isometric view of a cornerportion of the heating pad of FIG. 13 configured in accordance with anembodiment of the invention.

FIG. 15 is a partially schematic, top isometric view of a heating padconfigured in accordance with yet another embodiment of the invention.

FIG. 16 is a partially schematic, top isometric view of a heating padconfigured in accordance with yet another embodiment of the invention.

FIG. 17A is a top isometric view of a positioning/warming deviceconfigured in accordance with an embodiment of the invention.

FIG. 17B is a top isometric view of the positioning/warming device ofFIG. 17A supporting the legs of a patient in accordance with anembodiment of the invention.

FIG. 17C is a side cross-sectional view of the positioning/warmingdevice of FIG. 17A configured in accordance with an embodiment of theinvention.

FIG. 17D is a partially hidden top plan view of the positioning/warmingdevice of FIG. 17A configured in accordance with an embodiment of theinvention.

FIG. 18A is an isometric view of a patient warming system that includestwo armboards configured in accordance with an embodiment of theinvention.

FIG. 18B is an isometric view of a patient warming system that includesa roll configured in accordance with another embodiment of theinvention.

FIG. 18C is an end elevation view of a patient positioning/warmingdevice configured in accordance with yet another embodiment of theinvention.

FIG. 19 is a partially schematic, isometric view of a patient warmingsystem including one or more patient warming blankets configured inaccordance with another embodiment of the invention.

FIG. 20 is a partially schematic, isometric view of a patient warmingsystem configured in accordance with yet another embodiment of theinvention.

FIG. 21 illustrates a flow diagram of a routine for controlling thetemperature of a heating pad in accordance with an embodiment of theinvention.

FIG. 22 is an enlarged rear isometric view of the heating pad controlunit of FIG. 10 illustrating an attachment device configured inaccordance with an embodiment of the invention.

FIG. 23 is a schematic, partially cutaway, top isometric view of aheating pad configured in accordance with a further embodiment of theinvention.

FIGS. 24A-24D are enlarged top views of portions of heating elementsconfigured in accordance with embodiments of the invention.

FIG. 25 is an enlarged isometric view of a portion of the heatingelement of FIG. 23, configured in accordance with an embodiment of theinvention.

FIG. 26 is an enlarged side view of a conductive yarn configured inaccordance with an embodiment of the invention.

FIG. 27 is an enlarged, isometric cross-sectional view of a conductivestrand of the conductive yarn of FIG. 26, configured in accordance withan embodiment of the invention.

FIG. 28 is a flow diagram of a routine for providing power to a heatingelement in accordance with an embodiment of the invention.

FIG. 29A is partially cutaway top view of a heating sheet configured inaccordance with an embodiment of the invention.

FIG. 29B is an exploded side cross-sectional view of the heating sheetof FIG. 29A.

FIG. 30A is a partially exploded side view of a pan-down assembly havingan electronic module compartment configured in accordance with anembodiment of the invention.

FIG. 30B is a bottom view of the pan-down assembly of FIG. 30A.

DETAILED DESCRIPTION

The following disclosure describes various aspects of personal warmingsystems for use in hospitals and other nonmedical settings. In oneembodiment, a patient warming system configured in accordance with thepresent invention can include a heating pad configured to warm a patientpositioned on the pad in a step-wise fashion, allowing the temperatureto stabilize at each step before proceeding to the next step. One formof such step-wise warming can include warming the pad from 96.8° F. to98.6° F. in a first step, warming the pad from 98.6° F. to 100.4° F. ina second step, and warming the pad from 100.4° F. to 102.2° F. in athird and final step. In one aspect of this embodiment discussed ingreater detail below, warming the patient in a step-wise fashion mayprovide certain benefits over warming the patient directly from, forexample, 96.8° F. to 102.2° F.

In another embodiment, a patient warming system configured in accordancewith the invention can include a heating pad control unit having certainfeatures that facilitate use in hospital operating room (OR)environments. For example, in one aspect of this embodiment, the controlunit can include an exterior surface configured to deflect fluids thatcontact it. In addition, the control unit can have a center of gravity(CG) positioned to stabilize the control unit and prevent it frominadvertently tipping over during use. In a further embodiment, aheating pad control unit configured in accordance with the invention canalso include various features for quick and easy attachment to typicalOR structures. Such features can include, for example, a releasableclamp for quickly attaching the control unit to an IV pole so that thecontrol unit can be moved around an OR table as needed during anoperation. As discussed in greater detail below, many aspects ofembodiments of the invention are configured to meet or exceed one ormore of the IEC 60601 Standards for Medical Electrical Equipment as setforth by the U.S. Food and Drug Administration Center for Devices andRadiological Health.

In yet another embodiment, a patient warming system configured inaccordance with the invention can include one or more heating pads thatare at least generally radiolucent. The term radiolucent, as usedthroughout this disclosure, means that the particular structure istransparent, or at least generally transparent, to x-rays. One advantageof this embodiment is that such heating pads can be used to warmpatients during x-ray procedures without obscuring or otherwisepreventing acquisition of usable x-ray images. As discussed in greaterdetail below, such heating pads can include a number of radiolucentfeatures. Such features can include, for example, nonmetallic heatingelements, such as carbon ink-based heating elements, fiber optictemperature measurement devices, infrared temperature measurementdevices, thermally responsive state-changing devices, such as thermalchromatic devices, and other devices.

In a further embodiment, a patient warming system configured inaccordance with the invention can include one or more patientpositioning/warming devices. Such positioning/warming devices caninclude foam structures configured to position a selected portion of thepatient in a desired position or orientation to facilitate a medicalprocedure. In addition to having formed foam structures to position thepatient, such devices can also include one or more heating elementsconfigured to generate heat to warm the patient. These and other aspectsof the invention are described in detail below.

In yet another embodiment, a patient warming system configured inaccordance with aspects of the invention can include a heating elementthat is at least generally radiolucent. The heating element of thisembodiment can include a flexible substrate and a plurality ofconductive strands supported by the flexible substrate. Each of theconductive strands can include a core portion and a conductive portioncarried by the core portion. For example, in one embodiment, each of theconductive strands can include a non-conductive core portion, such asnylon, with metallic plating, such as silver plating. In anotherembodiment, the flexible substrate can include a fiber weave, and theplurality of conductive strands can be interwoven with the fiber weave.

In a further embodiment, a heating element configured in accordance withaspects of the invention can include a flexible substrate and at leastone conductive path defining a non-linear pattern extending across atleast a portion of the flexible substrate. The conductive path can beconfigured to generate heat by conducting electricity. In oneembodiment, the conductive path can define a repeating geometricpattern, such as a repeating “Greek key” pattern. In another embodiment,a plurality of at least generally linear conductive paths can extendacross at least a portion of the flexible substrate and intersect thenon-linear conductive paths.

As used throughout this disclosure, the term “patient warming device”will be understood by the reader to include not only systems andapparatuses suitable for warming patients in hospital settings, but alsosuch systems and apparatuses suitable for warming persons in non-medicalsettings.

As used throughout this disclosure, the term “heating pad” will beunderstood by the reader to include not only pads but mattresses,contoured support structures, and other structures configured to supportor otherwise contact a person's body or portions thereof. Additionally,throughout this disclosure, the term “medical procedures” will beunderstood by the reader to include therapeutic and diagnosticprocedures, as well as other types of medical-related activities.Accordingly, references throughout this disclosure to “patients” will beunderstood by the reader to also include persons undergoing suchtherapeutic and diagnostic procedures.

Certain specific details are set forth in the following description andin FIGS. 1-30B to provide a thorough understanding of variousembodiments of the invention. Other details describing well-knownstructures and systems are not set forth in the following description,however, to avoid unnecessarily obscuring the description of variousembodiments of the invention. The dimensions, angles, and otherspecifications shown in the following figures are merely illustrative ofparticular embodiments of the invention. Accordingly, other embodimentscan have other dimensions, angles, and specifications without departingfrom the spirit or scope of the invention. In addition, still otherembodiments of the invention can be practiced without several of thedetails described below.

In the figures, identical reference numbers identify identical or atleast generally similar elements. To facilitate the discussion of anyparticular element, the most significant digit or digits of anyreference number refer to the figure in which that element is firstintroduced. For example, element 110 is first introduced and discussedwith reference to FIG. 1.

FIG. 1 is a top isometric view of a patient warming system 100configured in accordance with an embodiment of the invention. In oneaspect of this embodiment, the patient warming system 100 includes aheating pad 110 having a heating element 150 operably connected to acontrol unit 120 via a utility cord 130. In the illustrated embodiment,the heating pad 110 is positioned on an OR table 101 in a typical ORsetting and the control unit 120 is positioned on the floor proximate tothe OR table 101. A patient (not shown) can be positioned on top of theheating pad 110 during a particular medical procedure, and the heatingpad 110 can provide warmth to the patient to prevent the patient's bodytemperature from dropping to an undesirably low level during theprocedure. In another aspect of this embodiment, the control unit 120can include a user interface 122 that allows an operator (not shown) tocontrol operation of the heating pad 110. For example, as discussed ingreater detail below, the user interface 122 can include one or moretemperature selectors that allow the operator to select a padtemperature, and one or more displays for presenting operatinginformation to the operator. Such operating information can include, forexample, the pad temperature proximate to the surface of the heating pad110.

FIG. 2 is a side elevational view of the control unit 120 of FIG. 1configured in accordance with an embodiment of the invention. In oneaspect of this embodiment, the control unit 120 includes a chassis 222having an upper portion 224 that supports the user interface 122. Theuser interface 122 can be sloped at an angle 225 such that fluids orother substances contacting the user interface 122 tend to flow offrather than remain and contaminate or obscure the surface. In oneembodiment, the angle 225 can be about 5 degrees. In other embodiments,the angle 225 can have other values. For example, in one otherembodiment, the angle 225 can be from about 5 degrees to about 15degrees. In a further embodiment, the user interface 122 can be at leastgenerally horizontal.

In another aspect of this embodiment, the chassis 222 further includes aplurality of sidewalls 226. In the illustrated embodiment, the sidewalls226 are canted slightly inboard toward the top portion of the controlunit 120 such that fluids and other substances contacting them will flowdownwardly and/or outwardly away from the control unit 120. For example,in one embodiment, the sidewalls 226 can be positioned at an angle 227relative to the horizontal. In one embodiment, the angle 227 can beabout 95 degrees. In other embodiments, the sidewalls 226 can bepositioned at other angles relative to the horizontal. For example, inone other embodiment, the angle 227 can be from about 95 degrees toabout 100 degrees. In another embodiment, the sidewalls 226 can be atleast generally vertical.

In a further aspect of this embodiment, the chassis 222 can also includean apron 240 positioned toward the bottom portion of the control unit120. The apron 240 can include a first angled surface 241 adjacent to asecond angled surface 242. Both the first and second angled surfaces241, 242 can be angled outwardly toward the bottom portion of thecontrol unit 120 to further cause fluids and other substances cascadingdown the sidewalls 226 to flow off the control unit 120. For example, inone embodiment, the first angled surface 241 can have a first angle 228of about 114 degrees from the horizontal, and the second angled surface242 can have a second angle 229 of about 95 degrees from the horizontal.In other embodiments, the first and second angles 228, 229 can haveother values. In a further embodiment, the apron 240 can be omitted.

In yet another aspect of this embodiment, the control unit 120 caninclude a compressible seal 230 extending peripherally around the baseportion of the control unit 120. The seal 230 can be configured torestrict or prevent fluids and other substances from moving underneaththe control unit 120. In one embodiment, the seal 230 can be positioneda distance 232 of about 0.12 inch above the floor on which the controlunit 120 is placed. In other embodiments, the distance 232 can haveother values. For example, in one other embodiment, the distance 232 canbe from about 0.05 inch to about 1.0 inch. In a further embodiment, theseal 230 can be configured to contact the floor. In yet anotherembodiment, the seal 230 can be omitted.

In a further aspect of this embodiment, the control unit 120 includes acenter of gravity (CG) 238 located a distance 236 above a plurality ofrollers 252. In the illustrated embodiment, the rollers 252 can bespaced apart by a distance 234, and the control unit 120 can beconfigured such that the CG distance 236 is equal to about one-half thedistance 234 between the rollers 252. Configuring the control unit 120in this manner can increase the stability of the control unit 120 toreduce the possibility of it being inadvertently tipped over during usein the OR environment. For example, configuring the control unit 120 inthe foregoing manner can result in a control unit that has to be tippedto an angle of at least about 45 degrees before it will tip over. Inother embodiments, the control unit 120 can have other configurationswithout departing from the spirit or scope of the present disclosure.For example, in other embodiments, the rollers 252 can be omitted andthe CG 238 can have other locations.

The foregoing description of the control unit 120 is provided heresolely to illustrate one embodiment of a control unit configured inaccordance with aspects of the present invention. Accordingly, controlunits configured in accordance with other embodiments of the inventioncan have features that differ from those described above withoutdeparting from the spirit or scope of the present invention.

FIG. 3 is a top view of the user interface 122 of the control unit 120taken substantially along line 3-3 in FIG. 2 in accordance with anembodiment of the invention. In one aspect of this embodiment, the userinterface 122 includes a standby indicator 374, a power selector 370,and a temperature unit selector 376. When the control unit 120 isoperably connected to an electrical source (such as a facilityelectrical outlet or an internal storage battery) and is switched “on,”the standby indicator 374 is illuminated indicating that the controlunit 120 is in the “standby” mode. In this mode, an operator can depressthe power selector 370 to cause the heating pad 110 (FIG. 1) to startwarming up. This action will also cause a power-on indicator 372 toilluminate providing a visual indication that the heating pad iswarming. As discussed in greater detail below, the operator can controlthe temperature of the heating pad 110 with one or more of a pluralityof temperature selectors 381-384. As the heating pad temperature rises,the temperature at the surface of the pad is displayed on a temperaturedisplay 371. The operator can choose between Centigrade or Fahrenheittemperature units by selectively depressing the temperature unitselector 376.

In another aspect of this embodiment, the temperature selectors 381-384allow the operator to choose from a range of heating pad temperaturesand select the temperature that best suits the particular circumstances.For example, the operator can choose a low temperature of 96.8° F.(selector 381), a medium temperature of 98.6° F. (selector 382), amedium-high temperature of 100.4° F. (selector 383), or a hightemperature of 102.2° F. (selector 384). Alternatively, the operator canelect to warm the patient in a step-wise manner using two or more of thetemperature selectors 381-384. Step-wise warming of a patient can beaccomplished in one embodiment as follows. Initially, the operator candepress the temperature selector 381 causing the surface of the heatingpad 110 to warm to a temperature of about 96.8° F. Once the pad'stemperature has stabilized at about 96.8° F. (as indicated by thetemperature display 371), the operator can depress the temperatureselector 382 to warm the heating pad to about 98.6° F. After the pad'stemperature has stabilized at about 98.6° F., the operator can depressthe temperature selector 383 to warm the pad to about 100.4° F.Step-wise warming of the patient in the foregoing manner may, undercertain circumstances, provide certain therapeutic benefits over directwarming of the patient from, for example, a temperature of about 88° F.to about 100.4° F.

Although step-wise patient warming has been described here using atemperature range from about 96.8° F. to about 100.4° F., in otherembodiments, the patient may be warmed using other temperature ranges inother manners. For example, in one other embodiment, the patient may bewarmed directly from an initial temperature to a selected padtemperature.

In a further aspect of this embodiment, the temperature range fieldsadjacent to the temperature selectors 381-384 can be different colors tovisually and intuitively indicate the associated temperature range. Forexample, in one embodiment, the “low temperature” field adjacent to thetemperature selector 381 can be blue in color to intuitively indicatecooler temperatures less than or equal to about 96.8° F. Similarly, the“medium temperature” field adjacent to the temperature selector 382 canbe green in color to intuitively indicate the normal body temperature ofabout 98.6° F. Further, the “medium-high temperature” field adjacent tothe temperature selector 383 can be yellow in color, and the “hightemperature” field adjacent to the temperature selector 384 can beorange in color to intuitively indicate temperatures that are somewhatabove normal body temperatures.

The present invention is not limited to the particular temperatureranges described above with reference to FIG. 3. Accordingly, in otherembodiments, heating devices in accordance with embodiments of theinvention can be operated at different temperatures in different rangeswithout departing from the spirit or scope of the present invention. Inaddition, in further embodiments the different temperature range optionscan be omitted and a heating device configured in accordance with thepresent invention can be operated at a single temperature.

In yet another aspect of this embodiment, the user interface 122includes a step-wise warming selector 385. The step-wise warmingselector 385 can be selected by an operator to automatically implement astep-wise patient warming program. For example, in one embodiment,selecting the step-wise warming selector 385 causes the surfacetemperature of the heating pad 110 (FIG. 1) to automatically increasefrom ambient room temperature to about 96.8° F. in a first step, fromabout 96.8° F. to about 98.6° F. in a second step, and from about 98.6°F. to 100.4° F. in a third step. In one aspect of this embodiment, theheating pad temperature can stabilize at each temperature level for apredetermined period of time before proceeding on to the nexttemperature level. In a further aspect of this embodiment, the timeperiod at which the heating pad 110 remains at each temperature levelcan be preselected by the operator. For example, in one embodiment, theoperator can choose to have the heating pad 110 maintain eachtemperature level for a period of about 10 minutes before proceeding tothe next level. In other embodiments, the operator can choose othertemperatures and other time periods to suit the particular situation.

In a further aspect of this embodiment, the control unit 120 can includeone or more alarms to alert the operator if the temperature of theheating pad 110 (FIG. 1) is greater than a selected range or of thesystem requires attention of some sort. In one embodiment, an audible orvisible alarm can activate when the heating pad 110 is operating abovethe temperature selected by the operator. When such a condition exists,an over temperature indicator 391 on the user interface 122 canilluminate. Similarly, if the heating pad 110 is operating in a lowbattery condition, then a battery low indicator 393 can illuminate. Inone embodiment, the battery low indicator 393 illuminates when there isone hour or less of stored power remaining in the battery. In thissituation, the operator can connect the control unit 120 to a suitableelectrical outlet to recharge the battery. In another embodiment, anaudible or visible alarm can activate when the patient warming system100 requires service. For example, when such a condition exists, aservice required indicator 392 on the user interface 122 can illuminate.In one aspect of this embodiment, illumination of the service requiredindicator 392 can indicate disconnection of a power cord providingelectrical power to the control unit 120.

As described in greater detail below, in one embodiment, the heating pad110 (FIG. 1) can include two or more temperature sensors configured todetermine the temperature proximate to the surface of the heating pad110. In one aspect of this embodiment, illumination of the servicerequired indicator 392 can also indicate a discrepancy between these twotemperature sensors. For example, in one embodiment, if one of thetemperature sensors measures a pad temperature that is more than about5° F. different from the other temperature sensor, then the servicerequired indicator 392 can illuminate to notify the operator of thediscrepancy. In response, the operator can investigate the source of thedisagreement between the two temperature sensors. In other embodiments,the service required indicator 392 can illuminate under other conditionsand for other reasons.

In a further embodiment, the user interface 122 can include an alarmmute selector 386. When selected, the alarm mute selector 386 causes oneor more of the alarms described above to be muted. For example, if thecontrol unit 120 includes an audible alarm that activates when theheating pad 110 exceeds a selected temperature, then selecting the alarmmute selector 386 causes the audible alarm to shut off. Similarly, thealarm mute selector 386 can also be depressed to turn off the servicerequired indicator 392. Alternatively, when the alarm mute selector 386is not selected, a system monitor indicator 387 is illuminatedindicating that the patient warming system 100 is being monitored. Inother embodiments, the alarm mute selector 386 can be configureddifferently or it can be omitted.

FIG. 4 is a partially hidden top isometric view of the heating pad 110of FIG. 1, configured in accordance with an embodiment of the invention.In one aspect of this embodiment, the heating pad 110 includes a cover112 and a connector housing or pan-down 410 sealably attached to thecover 112. The cover 112 can have a top portion 111 and a bottom portion113. The top portion 111 can include a cast-coated polyurethanefilm/polyurethane foam/polyester knit material. For example, in oneembodiment, the top portion 111 can include Staftex# COOLH/CPU 150material as supplied by Stafford Textiles Limited of Lakeshore Blvd. W.,Suite 308, Toronto, Ontario, Canada, M8V 1A4. In yet another aspect ofthis embodiment, the top portion 111 can include such material having athickness of about 0.08 mm (about 31.5 Mil) and having knownantibacterial properties FR to CA 117. In other embodiments, the topportion 111 can include other materials. In yet other embodiments, thebottom portion 113 can also include the foregoing cast-coatedpolyurethane film/polyurethane foam/polyester knit material.

In another aspect of this embodiment, the pan-down 410 provides a sealedconnection between the utility cord 130 and the power andinstrumentation lines 431-435 extending from the utility cord 130 to theheating element 150 and temperature sensors 460 and 462 within theheating pad 110. Although the power and instrumentation lines 431-435are shown in FIG. 4 as extending approximately down the middle of theheating pad 110, in other embodiments, the power and instrumentationlines 431-435 can extend down the sides of the heating pad 110 toimprove the radiolucency of the heating pad 110.

FIG. 5 is a partial cross-sectional side elevation view of the heatingpad 110 taken substantially along line 5-5 in FIG. 4 in accordance withan embodiment of the invention. In one aspect of this embodiment, theheating pad 110 includes an upper patient support portion or pad 140 anda lower patient support portion or pad 142 at least generallysandwiching the heating element 150. In one embodiment, the pads 140,142 can include foam materials and compressible foam materials at leastgenerally similar in structure and function to the corresponding foammaterials described in detail in U.S. patent application Ser. No.09/880,725, and U.S. Provisional Patent Application No. 60/374,853. Inother embodiments, the pads 140, 142 can include other foam materials.In still further embodiments, the pads 140, 142 (and, indeed, the otherfoam structures described below) can include other compressible and/orelastic materials that provide pressure relief and/or heat conduction.For example, in one embodiment, the pads 140, 142 can include a fibrousmaterial, such as a nylon fiber. In yet other embodiments, it isexpected that the pads 140, 142 can include yet other materials thathave pressure relief and heat conducting features similar to some foams.Thus, as will be appreciated by those of ordinary skill in the relevantart, aspects of the present invention are not limited to the use of foamin general or to the use of particular types of foam, but extend toother similar materials that demonstrate characteristics similar to thematerials disclosed herein.

The pan-down 410 can be a concave housing sealably attached to thebottom portion 113 of the cover 112, and the lower pad 142 can becontoured adjacent to the pan-down 410 to receive the pan-down 410 flushwith the bottom surface of the heating pad 110. Positioning the pan-down410 beneath the heating pad 110 in this manner can reduce the likelihoodof fluids and other substances contaminating the inner portions of theheating pad 110.

A first connector 504 can be mounted to the pan-down 410 and can beconnected to power lines 431 and 432 extending to the heating element150. Similarly, instrumentation lines 433, 434, and 435 can extend fromthe first connector 504 to the temperature sensors 460 and 462. In oneaspect of this embodiment, the temperature sensors 460, 462 can bepositioned at least approximately aligned along a centerline of theheating pad 110 so as to be adjacent to a patient's torso when thepatient (not shown) is positioned on the heating pad 110. Suchpositioning can prevent one or both of the temperature sensors 460, 462from becoming uncovered if the patient lifts a leg or other appendageoff the heating pad 110, which could happen if the sensors arepositioned laterally across the heating pad 110. In other embodiments,other temperature sensor orientations can be used.

A second connector 502 provided on one end of the utility cord 130 canmate to the first connector 504 to provide electrical connection betweenthe control unit 120 (FIG. 1) and the heating element 150 and thetemperature sensors 460 and 462. In one aspect of this embodiment thefirst connector 504 can be a male connector and the second connector 502can be a complimentary female connector. Using male connectors on boththe heating pad 110 and the control unit 120 avoids having to cleaninternal connector cavities on these components.

In still other embodiments of heating pads configured in accordance withthe invention, the first and second connectors 502, 504 can be omittedand the utility cord 130, or at least a portion of the utility cord 130,can pass directly through the pan-down 410. In these other embodiments,a nut or other sealing collar can attached the utility cord 130 to thepan-down 410 where the utility cord 130 passes through the pan-down 410.In addition, the utility cord 130 can include a pig-tail or other strainrelief feature proximate to the pan-down 410 to reduce the likelihood ofthe utility cord being pulled out of the pan-down 410.

In a further aspect of this embodiment, the cover 112 incorporating thepan-down 410 can be constructed by a method including the followingsteps: Cut the material to size for the top portion 111 and the bottomportion 113 of the cover 112. Sew two sides and one end of the top andbottom portions 111 and 113 together to form the cover 112 with one openend. Sonic bond the two sewn sides and the one sewn end. Cut out aportion of the bottom portion 113 to accept the pan-down 410. Glue theperiphery of the pan-down 410 to the bottom portion 113 of the cover112. Install the internal components of the heating pad 110 (e.g., theupper and lower pads 140 and 142, the heating element 150, etc.) andconnect the power and instrumentation lines 431-435 between the firstconnector 504 and the heating element 150 and the temperature sensors460, 462. Relieve the lower pad 142 to receive the pan-down 410 toensure a flat profile at the bottom surface of the heating pad 110. Onceall electrical connections have been verified and the electricalcomponents in the heating pad 110 have been verified as operational, sewthe last end (head end) of the cover 112 together. To ensure awaterproof seal, apply water barrier tape directly over sewn head endseam. Optionally use a heat gun to facilitate adhesion of the waterbarrier tape. In other embodiments, other methods for constructing thecover 112 can be used. For example, in one other embodiment, the cover112 can include a fluid-resistant zipper (not shown in FIG. 5) thatallows the cover 112 to be removed and replaced if contaminated ordamaged.

FIG. 6 is a cross-sectional side elevation view of the heating pad 110taken substantially along line 6-6 in FIG. 4. In one aspect of thisembodiment, the heating pad 110 includes a sleeve 670 at least partiallyenclosing the heating element 150. The sleeve 670 can include acarbon-fiber material such as Kevlar®. In other embodiments, the sleevecan include other materials. In a further aspect of this embodiment, thesleeve 670 can have a bottom portion 672 and a top portion 671. Thebottom portion 672 can include a woven fiberglass fabric laminated tothe sleeve 670 adjacent to the heating element 150. In otherembodiments, the woven fiberglass fabric can be omitted.

In another aspect of this embodiment, the heating element 150 caninclude a Mylar® polyester material with a copper foil bus embedded inconductive silver ink. For example, in one embodiment, the heatingelement 150 can include a DuPont Mylar® polyester that is 0.016 inchthick and has 70 micron-thick copper foil embedded in conductive carbonink (or, alternatively, silver ink). In this embodiment, the heatingelement 150 can utilize 24 volt power at 50 watts. Flexel InternationalLtd. of Queensway Industrial Estate, Glenrothes, Fife, Scotland, KY7 5QFis one source for portions of the heating element 150 configured inaccordance with this embodiment. For example, in one embodiment, theheating element 150 can include Mark IV type F heating element materialoffered by Flexel. In other embodiments, other materials can be used forthe heating element 150.

FIG. 7 is a schematic diagram of the control unit 120 and the heatingpad 110 of FIG. 1 configured in accordance with an embodiment of theinvention. In one aspect of this embodiment, the control unit 120 caninclude a connector receptacle 726, fuse holders 710, a transformer 720,a rectifier 702, pad relays 730 and 731, and the user interface 122. Aretractable power cord 724 can be received in the receptacle 726 tointroduce electrical power to the control unit 120. The receptacle 726can include a voltage selector 727 that, in one embodiment, allows anoperator to select between 115 volts and 230 volts. In one embodiment,the transformer 720 converts standard AC voltage from a hospitalfacility outlet to 24 volts DC. Power from the transformer 720 canproceed via the fuse holders 710, the rectifier 702, and the pad relays730 and 731 to the heating element 150 in the heating pad 110. In oneaspect of this embodiment, in-line fuses 752 can be employed to avoidelectrically overloading the circuit.

In one embodiment, the patient warming system shown schematically inFIG. 7 can be at least generally similar in structure and function tothe heating pad system described in pending U.S. patent application Ser.No. 09/880,725. In one aspect of this embodiment, however, the heatingpad 110 can include thermostats 704 and 706 that prevent the heating pad110 from exceeding a surface temperature of 41° C. In other embodiments,the thermostats 704 and 706 can be set at other temperatures or they canbe omitted. In yet another embodiment, activation of the thermostats 704and 706 can cause the over temperature indicator 391 shown in FIG. 3 toilluminate.

FIG. 8 is a schematic diagram of a control unit 820 and a heating pad810 configured in accordance with another embodiment of the invention.In one aspect of this embodiment, the heating pad 810 and the controlunit 820 can be portions of a gurney heating pad system. In anotheraspect of this embodiment, components of the control unit 820 can besubstantially similar to corresponding components of the control unit120 described above with reference to FIG. 7. Further, certain aspectsof the control unit 820 and the heating pad 810 can be substantiallysimilar to the power unit 220 and heating pad 210, respectively,described in pending U.S. patent application Ser. No. 09/880,725. In oneaspect of this embodiment, however, the control unit 820 can include aninternal power source 810 having batteries 802 and 804. In oneembodiment, the batteries 802 and 804 can include 12 amp-hour/12 VDCbatteries, such as Panasonic LC-R1212P batteries. In other embodiments,other power storage devices can be used.

The internal power source 810 can enable the heating pad 810 to functionindependently of an external power source, allowing the heating pad 810to be moved outside the range of fixed electrical outlets. The internalpower source 810 is connected to a charge relay 830 and a chargecontroller 840. When the control unit 820 is connected to an externalpower source (such as a facility electrical outlet) via a power cord824, power from the outside source flows to the batteries 802 and 804via the charge controller 840 and the charge relay 830 to recharge thebatteries 802 and 804 if need be. In addition, power from the outsidepower source flows to a transfer relay 820 and from there to the heatingpad 810 via pad relays 830 and 831. If, however, the control unit 820 isnot connected to an external power source, then the charge relay 830directs power from the batteries 802 and 804 to the heating pad 810 viathe transfer relay 820 and the pad relays 830 and 831. Accordingly, inthis manner, the heating pad 810 can use an external power source whenavailable and automatically switch to the internal power source 810 whenexternal power is not available.

FIG. 9 is an enlarged, partial cut away isometric view of the controlunit 120 of FIG. 1 configured in accordance with an embodiment of theinvention. In one aspect of this embodiment, the control unit 120includes a connector 904 that receives an external power cord 902. Adistal end (not shown) of the power cord 902 can be connected to anexternal power source, such as a facility electrical outlet, to provideelectrical power to the control unit 120. In a further aspect of thisembodiment, the connector 904 includes a fuse holder 906 and an on/offswitch 908. Once the power cord 902 has been connected to a suitablepower outlet, the control unit 120 can be powered up by switching theon/off switch 908 to the “on” position. If the control unit 120 is beingused with 15V external power (typical in the U.S.A.), then the fuseholder 906 can be configured to accommodate 115V power by orienting thefuse holder 906 in a first position in its receptacle. Conversely, ifthe control unit 120 is being used with 220V power (typical in Europe),then the fuse holder 906 can be configured to accommodate 220V byrotating the fuse holder 180 degrees from the 115V first position. Inyet another aspect of this embodiment, the control unit 120 includes ashield 910 positioned above the connector 904 to deflect fluids or othersubstances away from the connector 904 to prevent fluid ingress into thecontrol unit 120.

FIG. 10 is a top isometric view of a patient warming system 1000 thatincludes a number of patient warming devices configured in accordancewith an embodiment of the invention. In one aspect of this embodiment,the patient warming system 1000 includes a control system 1020configured to be carried by a typical OR structure such as an IV pole1002. The IV pole 1002 can provide mobility to the control system 1020to facilitate movement of the control system 1020 about the OR. Althoughthe main control unit 1021 and the accessory control unit 1022 a of theillustrated embodiment are attached to the IV pole 1002, these controlunits are further configured to attach to other structures. For example,such other structures can include tech stands, OR tables, beds, cribs orbassinets. This flexibility in attachment offers versatility for use ofthese respective control units and the associated heating pads in an OR,a PACU, a burn unit, or a neonatal care unit.

In the illustrated embodiment, the control system 1020 includes a firstor main control unit 1021 and a second or accessory control unit 1022 a.The main control unit 1021 can be at least generally similar instructure and function to the control unit 120 described above withreference to FIGS. 1-9. Further, the main control unit 1021 can also beat least generally similar in structure and function to one or more ofthe control units described in pending U.S. patent application Ser. No.09/880,725, or in pending U.S. Provisional Patent Application No.60/374,853.

The main control unit 1021 can receive standard AC power from a hospitalelectrical outlet or other source via a power cord 1004. The maincontrol unit 1021 can in turn provide power and control signals to aheating pad 1010 positioned on the OR table 101 via a utility cord 1030.In a further aspect of this embodiment, the heating pad 1010 can be atleast generally similar in structure and function to the heating pad 110described above with reference to FIGS. 1-9. In other embodiments asdescribed below, however, the heating pad 1010 may differ from theheating pad 110.

In addition to providing power and control signals to the heating pad1010, the main control unit 1021 can also provide power to the accessorycontrol unit 1022 a via an accessory cable 1032. The accessory controlunit 1022 a can include a plurality of outlets 1023 a, b for providingpower to one or more additional patient warming devices. For example, inthe illustrated embodiment, the accessory control unit 1022 a providespower to a first patient warming device 1011 via a first cable 1034 a,and to a second patient warming device 1012 via a second cable 1034 b.As explained in greater detail below, the patient warming devices 1011and 1012 can include one or more foam portions at least partiallyenclosing heating elements that receive power via the cables 1034 a, b.In addition to providing warmth to the patient, the warming devices 1011and 1012 can also be shaped and sized to position the patient inselected orientations to facilitate various types of medical procedures.This feature can enable a practitioner to position a patient in such away as to facilitate a particular medical procedure without compromisingthe patient's body temperature.

The patient warming system 1000 can include a number of features toenhance its versatility in an OR environment. In one embodiment, forexample, each of the different patient warming devices 1010, 1011, and1012 can be set to a different temperature if desired by the medicalpractitioner to, for example, facilitate a particular procedure orinduce a particular therapeutic effect. In other embodiments, each ofthe patient warming devices can be set to the same temperature. Thus,various portions of the patient's body can be maintained at differenttemperatures or the same temperature depending on the particularapplication.

FIG. 11A is an enlarged front view of the accessory control unit 1022 aof FIG. 10 configured in accordance with an embodiment of the invention,and FIG. 11B is an enlarged front view of an accessory control unit 1022b configured in accordance with another embodiment of the invention.Referring first to FIG. 11A, in one aspect of this embodiment, theaccessory control unit 1022 a includes a first temperature display 1124a and a second temperature display 1124 b. The first temperature display1124 a can be configured to display a temperature of the patient warmingdevice 1011 (FIG. 10) connected to the accessory control unit 1022 a viathe first cable 1034 a. Similarly, the second temperature display 1124 bcan be configured to display a temperature of the patient warming device1012 (FIG. 10) connected to the accessory control unit 1022 a via thesecond cable 1034 b. In another aspect of this embodiment, the accessorycontrol unit 1022 a may not include separate temperature selectors forindependently controlling the temperatures of the patient warmingdevices 1011 and 1012. Accordingly, in this embodiment, an operator canselect temperatures for the patient warming devices 1011 and 1012 withthe main control unit 1021 of FIG. 10 as described above, for example,with reference to FIG. 3. As a result, in this embodiment, each of thepatient warming devices 1010, 1011, and 1012 is controlled at the sametemperature by the main control unit 1021.

In a further aspect of this embodiment, the accessory control unit 1022a can also include a power selector 1125 and a warning indicator 1127.The power selector 1125 can be used to turn the accessory control unit1022 a on and off. In other embodiments, the power selector 1125 can beomitted and the accessory control unit 1022 a may become activeimmediately upon connection to the control system 1020. In oneembodiment, the warning indicator 1127 can be a light that isilluminated if the temperature of one or more of the patient warmingdevices 1010, 1011 and 1012 exceeds the selected temperature. In otherembodiments, the warning indicator 1127 can be omitted.

Referring now to FIG. 11B, in one aspect of this embodiment, theaccessory control unit 1022 b includes a first control set 1128 a forindependently controlling the temperature of a first patient warmingdevice, and a second control set 1128 b for independently controllingthe temperature of a second patient warming device. In one aspect ofthis embodiment, one or more of the features of the accessory controlunit 1022 b can be at least generally similar in structure and functionto corresponding features of the user interface 122 described above withreference to FIG. 3. Further, one or more of the features of theaccessory control unit 1022 b can also be at least generally similar instructure and function to corresponding features of the control unitsdescribed in pending U.S. patent application Ser. No. 09/880,725, or inpending U.S. Provisional Patent Application No. 60/374,853. For example,the control sets 1128 can each include a temperature display and aplurality of temperature selectors. The temperature selectors caninclude a low temperature selector (e.g., 96.8° F.), a mediumtemperature selector (e.g., 98.6° F.), medium-high temperature selector(e.g., 100.4° F.), and a high temperature selector (e.g., 102.2° F.). Inother embodiments, the control sets 1128 can include other temperatureoptions.

Although the accessory control units 1022 a, b described above areconfigured to accommodate two patient warming devices via the outlets1023 a, in other embodiments, accessory control units configured inaccordance with the present invention can accommodate more or fewerpatient warming devices without departing from the spirit or scope ofthe present invention. For example, in another embodiment, an accessorycontrol unit configured in accordance with the present invention canaccommodate three or more patient warming devices. In this embodiment,the patient warming devices may be used to warm two or more patientspositioned on multiple OR tables. In a further embodiment, such anaccessory control unit may accommodate only a single patient warmingdevice. Thus, accessory control units configured in accordance with thepresent invention for controlling patient warming devices and, morespecifically, for controlling patient warming and positioning devices,are not limited to the particular embodiments described herein.

FIG. 12 is an exploded, partially hidden, partially cut away topisometric view of a heating pad 1210 configured in accordance withanother embodiment of the invention. In one aspect of this embodiment,the heating pad 1210 includes a heating element 1250 positioned at leastgenerally between a first foam portion 1240 and a second foam portion1242. The first foam portion 1240 can include a viscoelastic foam havinga thickness of about 1 inch. In other embodiments, the first foamportion 1240 can include other types of foam having other thicknesses.In another aspect of this embodiment, the second foam portion 1242 caninclude a high-density polyurethane foam having a thickness of about 2.5inches. In other embodiments, the second foam portion 1242 can includeother types of foam having other thicknesses.

In a further aspect of this embodiment, the heating element 1250 caninclude a first bus bar or first lead 1253 and a second bus bar orsecond lead 1255 positioned along opposite edges of a flexible supportmember 1251. In the illustrated embodiment, the flexible support member1251 includes a first film layer 1252 a and a second film layer 1252 b.In one embodiment, the film layers 1252 can include a polyester film. Inother embodiments, the film layers 1252 can include other materials. Inanother aspect of this embodiment, the first and second leads 1253, 1255can include a conductive material such as copper material. For example,in one embodiment, the first and second leads 1253, 1255 can includebraided copper, braided silver, or other metallic and non-metallicconductive materials.

In yet another aspect of this embodiment, the heating element 1250 canfurther include electrically conductive carbon ink portions 1254extending between the first lead 1253 and the second lead 1255.Accordingly, when each of the leads 1253, 1255 is biased at a differentelectrical potential, the carbon ink portions 1254 can conductelectrical current across the heating element 1250 to generate heat forwarming the heating pad 1210. One advantage of using carbon ink in thismanner is that it is at least generally radiolucent. As a result, itwill not obscure or otherwise impair x-ray images taken of a patientpositioned on the heating pad 1210.

In a further aspect of this embodiment, the heating element 1250 orportions thereof can be provided by Flexel International, Ltd.Corporation of Scotland. In other embodiments, the heating element 1250or portions thereof can include a silver oxide conductive materialprovided by Green Textiles, Inc. of South Carolina, U.S.A. In yetanother embodiment, the heating element 1250 or portions thereof caninclude Gorix material from England. In still further embodiments, theheating element 1250 can include materials and components in differentconfigurations and from different sources without departing from thespirit or scope of the present disclosure. For example, in anotherembodiment, it is expected that the heating element 1250 can includecarbon strands woven in a cloth substrate, such as GVP material fromItaly.

In another aspect of this embodiment, the heating pad 1210 can include aconnector housing or pan-down 1209 configured to introduce power and/orinstrumentation lines from a utility cord 1230 into the heating pad1210. As discussed in greater detail below, the heating pad 1210 canalso include a form-fitting and fluid-resistant cover 1212 to which thepan-down 1209 is sealably attached. Further, the second foam portion1242 can be recessed or locally contoured to receive the pan-down 1209in such a way that the heating pad 1210 will sit at least generally flaton an OR table or other supporting surface.

Power lines 1231, 1232 pass from the utility cord 1230 into the heatingpad 1210 via the pan-down 1209. In a further aspect of this embodiment,the first power line 1231 can be operatively connected to the first lead1253 and can be configured to bias the first lead 1253 at +24 VDC.Similarly, the second power line 1232 can be operatively connected tothe second lead 1255 and can be configured to bias the second lead 1255at −24 VDC. Accordingly, when the utility cord 1230 is connected to asuitable power source (such as the main control unit 1021 describedabove with reference to FIG. 10), the power lines 1231 and 1232 bias therespective leads 1253, 1255 at different potentials causing current toflow between the leads 1253, 1255 via the carbon ink portions 1254.

Instrumentation lines 1233, 1234, and 1235 extend from the pan-down 1209through adjacent portions of foam to a first temperature sensor 1260 anda second temperature sensor 1262. The first and second temperaturesensors 1260, 1262 can be configured to sense the temperature proximateto the top surface of the first foam portion 1240. As described above,the sensed temperature can be displayed for viewing by a practitioner oroperator on the user interface 122 of the control unit 120 (FIGS. 1-3).In a further aspect of this embodiment, the first foam portion 1240 canbe configured to support the first and second temperature sensors 1260,1262 toward the top surface of the first foam portion 1240. In oneembodiment, the first and second temperature sensors 1260, 1262 can beresistive thermal devices (RTDs) provided by the Minco Corporation. Inother embodiments, other temperature sensors can be used. For example,in another embodiment described in greater detail below, the heating pad1210 can include one or more radiolucent temperature sensing devices.

In yet another aspect of this embodiment, the heating pad 1210 canfurther include a number of backup safety devices to prevent the heatingpad 1210 from exceeding a selected temperature range. For example, inthe illustrated embodiment, the heating pad 1210 can include a pluralityof first thermostats 1204 connected in a series with the first powerline 1231, and a plurality of second thermostats 1206 connected in aseries with the second power line 1232. In one embodiment, thethermostats 1204, 1206 can include snap-acting thermostats. In otherembodiments, the thermostats 1204, 1206 can include other devices. Thefirst plurality of thermostats 1204 can be configured to activate (i.e.,open the corresponding circuit) if the heating element 1250 reaches apreselected over-temperature condition. For example, in one embodiment,the first plurality of thermostats 1204 can be configured to activate ifthe temperature of the heating element 1250 exceeds 49° C. If thistemperature is exceeded, then one or more of the first plurality ofthermostats 1204 can activate, thereby cutting power to the first lead1253 and stopping the generation of heat.

In yet another aspect of this embodiment, the second plurality ofthermostats 1206 can be configured to activate if the temperatureproximate to the upper surface of the first foam portion 1240 exceeds apreselected temperature. For example, in one embodiment, the secondplurality of thermostats 1206 can be configured to activate if the uppersurface of the first foam portion 1240 exceeds 41° C. If thistemperature is exceeded, then one or more of the second plurality ofthermostats 1206 can activate, thereby cutting power to the second lead1255 and stopping the generation of heat. The first foam portion 1240can be dimpled or otherwise contoured to receive the plurality of secondthermostats 1206 so that they will not be felt by a patient positionedon top of the heating pad 1210.

An operator (not shown) can use the heating pad 1210 to warm a patient(also not shown) in one embodiment as follows. First, the operatorselects a desired heating pad temperature with, for example, the userinterface 122 on the control unit 120 (FIGS. 1-3). The first and secondtemperature sensors 1260, 1262 then sense the temperature proximate tothe surface of the heating pad 1210 and communicate this information tothe control unit 120. If at any time during operation the surfacetemperature of the heating pad 1210 exceeds the selected temperature,the control unit 120 can shut off power to the heating element 1250until the surface of the heating pad 1210 cools down to the selectedtemperature. Once the temperature falls to the selected temperature, thecontrol unit 120 can continue applying power to the heating element 1250to maintain the selected temperature. Thus, in this embodiment, thefirst and second temperature sensors 1260, 1262 are part of a primarytemperature control circuit that modulates power to the heating element1250 in response to the measured temperature proximate to the surface ofthe heating pad 1210.

In another embodiment, the plurality of second thermostats 1206 can makeup a backup temperature control circuit for the heating pad 1210. Forexample, as mentioned above, the plurality of second thermostats 1206can be configured to activate and open the corresponding electricalcircuit to the second lead 1255 if the temperature at the surface of theheating pad 1210 exceeds a preselected temperature. For example, if thehighest possible temperature that the operator of the heating pad 1210can select is 39° C., then the second plurality of thermostats 1206 canbe configured to activate if the surface of the heating pad 1210 reaches41° C. In this way, the second plurality of thermostats 1206 will notactivate unless the primary temperature control circuit (i.e., the firstand second temperature sensors 1260, 1262) fails.

As yet another backup temperature control circuit, the plurality offirst thermostats 1204 can be configured to activate if the temperatureproximate to the surface of the heating element 1250 exceeds apreselected temperature that is higher than the activation temperatureof the plurality of second thermostats 1206. For example, if theplurality of second thermostats 1206 are configured to activate at 41°C., the plurality of first thermostats 1204 can be configured toactivate at 49° C. Thus, if the primary temperature control circuitprovided by the first and second temperature sensors 1260, 1262 fails,and the backup circuit provided by the plurality of second thermostats1206 also fails, then the plurality of first thermostats 1204 canactivate to open the corresponding electrical circuit and cut power tothe heating element 1250.

The temperature control circuits described above are provided here toillustrate one method for controlling the temperature of the heating pad1210 in accordance with the present invention. However, the invention isnot limited to the particular embodiment described. Accordingly, inother embodiments, other temperature sensors and/or other thermostatscan be used to provide primary and backup temperature control circuitsconfigured in accordance with the present invention.

In yet another aspect of this embodiment, the heating element 1250 canbe at least partially enclosed within a first sleeve 1270. In oneembodiment, the first sleeve 1270 can include carbon fiber material suchas Kevlar®. In other embodiments, the first sleeve 1270 can includeother materials. In a further aspect of this embodiment, the heating pad1210 can also include a second sleeve 1272 configured to at leastpartially enclose the first and second foam portions 1240, 1242 and theheating element 1250. In one embodiment, the second sleeve 1272 caninclude carbon fiber material such as Kevlar®. In other embodiments, thesecond sleeve 1272 can include other materials. In yet anotherembodiment, the first sleeve 1270 and/or the second sleeve 1272 can beomitted.

In a further aspect of this embodiment, the cover 1212 can extend overthe second sleeve 1272. In one embodiment, the cover 1212 can include anantimicrobial, abrasion-resistant and comfortable fabric, such as Kodyfabric. The cover 1212 can further include a fluid-resistant zipper 1213extending longitudinally on a lower surface of the cover 1212 tofacilitate its removal.

FIG. 13 is a partially cut away, top isometric view of a heating pad1310 configured in accordance with another embodiment of the invention.Many elements of the heating pad 1310 can be at least generally similarin structure and function to the heating pad 1210 discussed above withreference to FIG. 12. For example, the heating pad 1310 can include aheating element 1350 sandwiched between a first foam portion 1340 and asecond foam portion 1342. The first foam portion 1340 may be relativelythin in this embodiment and may have a thickness of from about 0.12 inchto about 1 inch. In another embodiment, the first foam portion 1340 canhave a thickness of about 0.50 inch. In further embodiments, the firstfoam portion 1340 may have other thicknesses or it can be omitted.

The heating element 1350 can be at least generally similar in structureand function to the heating element 1250 described above with referenceto FIG. 12. For example, the heating element 1350 can include a firstbus bar or first lead 1353 extending proximate to a first edge 1357 ofthe heating element 1350, and a second bus bar or second lead 1355extending proximate to a second edge 1359 of the heating element 1350.In a further aspect of this embodiment, however, the first and secondedges 1357, 1359 of the heating element 1350 are folded downward alongthe sides of the second foam portion 1342. One advantage of this featureis that it orients the leads 1353, 1355 edgewise on the outer peripheryof the heating pad 1310 so that the majority of the heating pad 1310remains radiolucent to facilitate x-ray imaging of a patient positionedon the heating pad 1310.

In a further aspect of this embodiment, the heating pad 1310 can includea number of features that enhance its radiolucent characteristics tofacilitate its use in warming patients undergoing x-ray examinations,such as x-ray exams occurring during a typical cardiac catheterizationprocedure. For example, in the illustrated embodiment, the heating pad1310 can include a first or primary temperature control circuit 1381 anda second or backup temperature control circuit 1382 that are both atleast generally radiolucent. The primary temperature control circuit1381 can include a first radiolucent temperature sensing device 1384(“first radiolucent device 1384”) operably connected to a heating padcontrol unit 1320 by a first radiolucent cable 1385. The firstradiolucent device 1384 can be positioned at least proximate to theupper surface of the first foam portion 1340. In one aspect of thisembodiment, the first radiolucent device 1384 can include a fiber optictemperature sensor. In other embodiments, it is expected that the firstradiolucent device 1384 can include other types of radiolucent, or atleast generally radiolucent, temperature sensing devices.

In another aspect of this embodiment, the first radiolucent cable 1385can include a fiber optic cable for communicating temperatureinformation from the first radiolucent device 1384 to the control unit1320. In other embodiments, it is expected that the first radiolucentcable 1385 can include other radiolucent, or at least generallyradiolucent, cables suitable for communicating temperature informationfrom the first radiolucent device 1384 to the control unit 1320. In yetother embodiments, it is expected that the heating pad 1310 can includeone or more wireless devices for communicating temperature informationfrom the heating pad 1310 to the control unit 1320 or, alternatively,for communicating temperature control inputs from the control unit 1320to the heating element 1350.

When the first radiolucent device 1384 includes a fiber optictemperature sensing device, the control unit 1320 can include a fiberoptic controller 1322 configured to convert the optical signal receivedfrom the fiber optic device into an electric signal usable by thecontrol unit 1320. The first radiolucent device 1384 can be operablyconnected to the fiber optic controller 1322 via a pan-down or othersuitable connector 1309 (shown schematically in FIG. 13).

When the heating element 1350 is operating, the first radiolucent device1384 can sense the temperature proximate to the surface of the heatingpad 1310 and communicate temperature information to the control unit1320 via the first radiolucent cable 1385. The control unit 1320 canthen display the heating pad temperature as described above withreference to, for example, FIG. 3, for viewing by an operator orpractitioner (not shown). Further, the control unit 1320 can use thetemperature information received from the first radiolucent device 1384to control the temperature of the heating element 1350. For example, ifthe first radiolucent device 1384 determines that the temperatureproximate to the surface of the heating pad 1310 exceeds the temperatureselected by the operator, then the control unit 1320 can cut off powerto the heating element 1350 until the temperature drops down to theselected temperature.

In another aspect of this embodiment, the backup temperature controlcircuit 1384 can include a second radiolucent temperature sensing device1386 (“second radiolucent device 1386”) operably connected to thecontrol unit 1320 by a second radiolucent cable 1389. In one aspect ofthis embodiment, the second radiolucent device 1386 can include athermally responsive media such as a thermal chromatic liquid crystal(TLC) that changes state at a predetermined temperature. In otherembodiments, it is expected that the second radiolucent device 1386 caninclude other types of radiolucent, or at least generally radiolucent,temperature sensing and/or thermally responsive state-changing devices.For example, in one other embodiment, the second radiolucent device 1386can include a fiber optic temperature sensor at least generally similarto the first radiolucent device 1384. One source of such fiber optictemperature sensors may include Photon Control, Inc. of 8540 BaxterPlace, Burnaby, B.C., Canada V5A 4T8, among other sources.

In a further aspect of this embodiment, the second radiolucent cable1389 can include at least one fiber optic cable for communicatingtemperature information from the second radiolucent device 1386 to anelectronic module 1387 embedded toward a lower corner of the heating pad1310. For example, in the illustrated embodiment, the second radiolucentcable 1389 includes a first fiber optic tube 1388 a and a second fiberoptic tube 1388 b extending between the second radiolucent device 1386and the electronic module 1387. The electronic module 1387 can beoperably connected to the control unit 1320 to receive electrical powerfrom the control unit 1320. In addition, the electronic module 1387 canbe operably connected to the first lead 1353 by a first power line 1331and to the second lead 1355 by a second power line 1332.

In operation, the electronic module 1387 acts like a switch thatcontrols power to the first and second leads 1353, 1355 in response tochanging light signals received from the second radiolucent device 1386via the second fiber optic tube 1388 b. For example, when the secondradiolucent device 1386 includes a TLC, the electronic module 1387 canemit a light signal through the first fiber optic tube 1388 a to theTLC. The light signal can pass through the TLC and return to theelectronic module 1387 via the second fiber optic tube 1388 b. If theTLC changes state in response to reaching a predetermined temperature,the light signal returning to the electronic module 1387 via the secondfiber optic tube 1388 b will change accordingly. The electronic modulecan then cut power to the leads 1353, 1355 on the heating element 1350in response to receiving the changed light signal.

In operation, the primary temperature control circuit 1381 can be usedto limit the temperature of the heating pad 1310 to a first operatingrange, and the backup temperature control circuit 1382 can be used tolimit the temperature of the heating pad 1310 to a second highertemperature range in the event that the primary temperature controlcircuit 1381 fails. For example, in this embodiment, an operator selectsa heating pad temperature with the control unit 1320 and power istransmitted to the heating element 1350 via the first and second powerlines 1331, 1332. As the heating pad 1310 warms up, the firstradiolucent device 1384 senses the temperature proximate to the surfaceof the heating pad 1310 and communicates this information to the controlunit 1320 via the first radiolucent cable 1385. If the sensedtemperature exceeds the selected temperature, then the control unit 1320cuts off power to the heating element 1350 until the temperatureproximate to the surface of the heating pad 1310 drops to, or below, theselected temperature. At such time, the control unit 1320 resumestransmitting power to the heating element 1350. In this manner, thetemperature proximate to the surface of the heating pad 1310 ismaintained at or near the selected temperature.

If the primary temperature control circuit 1381 fails, then the heatingpad 1310 may continue to warm above and beyond the selected temperature.If this happens and the temperature proximate to the surface of theheating pad 1310 reaches or exceeds the threshold temperature at whichthe second radiolucent device 1386 is activated (e.g., changes state),then the second radiolucent device 1386 will interrupt or otherwisechange the light signal received from the electronic module 1387 via thefirst fiber optic tube 1388 a. The changed light signal will then returnto the electronic module 1387 via the second fiber optic tube 1388 b.The change in the light signal returning to the electronic module 1387will cause the electronic module 1387 to cut off power to the heatingelement 1350 until the temperature proximate to the surface of theheating pad 1310 drops to, or below, the selected temperature.

In a further aspect of this embodiment, the primary temperature controlcircuit 1381 can be configured to control the temperature proximate tothe surface of the heating pad 1310 to within a first range of, forexample, +2° F. above the selected temperature, and the backuptemperature control circuit 1382 can be configured to control thetemperature proximate to the heating element 1350 to within a secondhigher range of, for example, +10° C. above the selected temperature.Thus, in this embodiment, if the primary temperature control circuit1381 fails, then the backup temperature control circuit 1382 willprevent the heating pad 1310 from exceeding the selected temperature bymore than 10° C. These temperature control limits provided here are forpurposes of illustration only. Accordingly, in other embodiments, theprimary and backup temperature control circuits 1381, 1382 can haveother temperature control limits. In one other embodiment, the primaryand backup temperature control circuits 1381, 1382 can have the sametemperature control limit.

One feature of the embodiments of the invention illustrated in FIG. 13is that the heating element 1350, the primary temperature controlcircuit 1381, and the secondary temperature control circuit 1382 are allat least generally radiolucent. One advantage of this feature is thatthe heating pad 1310 can be used to warm and support a patientundergoing a full-body x-ray exam, such as an x-ray exam associated witha cardiac catheterization procedure, and the heating pad 1310 will notobscure or otherwise appreciably impair the x-ray imaging.

FIG. 14 is a partially schematic, enlarged, top isometric view of acorner portion of the heating pad 1310 of FIG. 13 configured inaccordance with an embodiment of the invention. In one aspect of thisembodiment, the electronic module 1387 can be embedded in a lower cornerof the second foam portion 1342. In other embodiments, the electronicmodule 1387 can be located in other positions. For example, in one otherembodiment, the electronic module 1387 can be located outside of theheating pad 1310. The fiber optic tubes 1388 a, b can extend from theelectronic module 1387 to the second radiolucent device 1386. The secondradiolucent device 1386 can be positioned at least proximate to theheating element 1350. For example, in the illustrated embodiment, thesecond radiolucent device 1386 is positioned at least generally on topof the heating element 1350. In other embodiments, the secondradiolucent device 1386 can be positioned at other locations within theheating pad 1310.

In another aspect of this embodiment, a pan-down 1409 can be embedded inthe second foam portion 1342 adjacent to the electronic module 1387. Autility cord 1430 extending from the control unit 1320 (not shown inFIG. 14) to the pan-down 1409 can include a cable 1485 and four powerlines 1431-1434. The utility cord 1430 can be coupled to a connector onthe pan-down 1409 so that the cable 1485 is operably connected to thefirst radiolucent cable 1385 extending from the pan-down 1409 to thefirst radiolucent device 1384 (not shown in FIG. 14). The utility cord1430 can be similarly coupled to the connector on the pan-down 1409 sothat the power lines 1431-1434 are operably connected to correspondingpower lines 1441-1444 extending from the pan-down 1409 to the electronicmodule 1387. The power lines 1441 and 1442 can provide power to theelectronic module 1387 from the control unit 1320. The power lines 1443and 1444 can provide power to the leads 1353, 1355 via the electricmodule 1387. In other embodiments, other methods and structures can beused to operably connect the control unit 1320 to the various devicespositioned within the heating pad 1310.

FIG. 15 is a partially schematic, top isometric view of a heating pad1510 configured in accordance with yet another embodiment of theinvention. An upper foam portion of the heating pad 1510 is omitted inFIG. 15 for purposes of clarity. Portions of the heating pad 1510 can beat least generally similar in structure and function to correspondingportions of the heating pad 1310 described above with reference to FIGS.13 and 14. In one aspect of this embodiment, however, a secondradiolucent device 1586 used in a backup temperature control circuit1582 can include a plurality of fiber optic pipe strands 1587 (shown asa first fiber optic pipe strand 1587 a and a second fiber optic pipestrand 1587 b). It is expected that use of multiple fiber optic pipestrands will allow temperature averaging across a heating element 1350.

FIG. 16 is a partially schematic, top isometric view of a heating pad1610 configured in accordance with yet another embodiment of theinvention. An upper foam portion of the heating pad 1610 is omitted inFIG. 16 for purposes of clarity. In one aspect of this embodiment, theheating pad 1610 includes an infrared sensor 1690 as an additionalbackup temperature control device. In this embodiment, the infraredsensor 1690 can be used to monitor and control the temperature of aheating element 1650 in the event that both a primary temperaturecontrol circuit 1681 and a backup temperature control circuit 1682 fail.(The primary and backup temperature control circuits 1681, 1682 can beat least generally similar in structure and function to the primary andbackup temperature control circuits 1381, 1382, respectively, describedabove with reference to FIG. 13.) As will be apparent to those ofordinary skill in the relevant art, radiolucent temperature controldevices in accordance with the present invention are not limited to thefiber optic or infrared temperature sensors disclosed herein.Accordingly, in other embodiments, other radiolucent, or at leastgenerally radiolucent, temperature control devices can be used tocontrol the temperature of heating pads configured in accordance withthe present disclosure.

FIGS. 17A-D illustrate a patient positioning/warming device configuredin accordance with an embodiment of the invention. Thepositioning/warming device of the illustrated embodiment may be a legpositioning device configured to facilitate the harvest of veins from apatient's leg for use in heart surgery or another medical procedure.This particular positioning/warming device configuration is presentedhere only to illustrate selected aspects of the invention. Accordingly,as will be explained in greater detail below, in other embodimentspatient positioning/warming devices in accordance with the invention canhave other configurations.

FIG. 17A is a top isometric view of a positioning/warming device 1740configured in accordance with an embodiment of the invention. In oneaspect of this embodiment, the positioning/warming device 1740 receiveselectrical power via a power line 1734 (from, e.g., a control unit suchas the accessory control unit 1022 a of FIG. 10). In the illustratedembodiment, the positioning/warming device 1740 includes a firstcontoured portion 1742 a and a second contoured portion 1742 b. As shownin FIG. 17B, the first and second contoured portions 1742 a, b areconfigured to receive the legs of a patient P and provide warmth to thelegs while positioning them in a favorable orientation for harvestingveins or for conducting other medical procedures.

FIG. 17C is a side cross-sectional view, and FIG. 17D is a partiallyhidden top plan view, of the positioning/warming device 1740 configuredin accordance with an embodiment of the invention. Referring to FIGS.17C and D together, in one aspect of this embodiment, thepositioning/warming device 1740 includes a heating element 1750, innerfoam portions 1746 a, b, and outer foam portions 1744 a, b. The heatingelement 1750 can be at least generally similar in structure and functionto one or more of the heating elements described in detail above. Thefoam portions 1746, 1744 can be selected depending on a number offactors including, for example, pressure reduction and heat retentionparameters. In one embodiment, for example, the inner foam portions 1746may be denser than the outer foam portions 1744 to retain the heat fromthe heating element 1750. In this embodiment, at least one of the innerfoam portions 1746 can be a viscoelastic foam selected and positioned toact as a heat reservoir efficiently retaining heat generated by theheating element 1750. In another aspect of this embodiment, the outerfoam portions 1744 can be selected from a number of different types ofviscoelastic foam designed for pressure reduction and patient comfort.In other embodiments, the inner and outer foam portions 1746, 1744 caninclude foams having the same densities. In yet other embodiments, oneor more of the inner foam portions 1746, or alternatively, one or moreof the outer foam portions 1744, can be omitted from thepositioning/warming device 1740.

The foam selected for use in the positioning/warming device 1740 can becontoured to provide a desired shape for patient positioning using anumber of different methods. In one embodiment, the foam can be formedby injection molding with an appropriate mold. In another embodiment,the foam can be machined or otherwise cut to provide the desired shape.

In a further aspect of this embodiment, the positioning/warming device1740 can include a fluid-resistant and antimicrobial cover 1748. In oneembodiment, the cover 1748 can be a spray-on coating that can be easilycleaned. In another embodiment, the cover 1748 can include a durablefabric material shaped and sized to fit neatly around the contoured foamportions 1744, 1746.

In one embodiment, the patient positioning/warming device 1740 caninclude one or more temperature sensors 1756 for providing temperaturefeedback to the corresponding control unit. The temperature sensors 1756and associated systems can be at least generally similar in structureand function to the temperature sensors and associated feedback circuitsdescribed in U.S. patent application Ser. No. 09/880,725 and U.S.provisional patent application No. 60/374,853. The temperature sensorcircuit can provide a means for preventing the temperature proximate tothe surface of the pad from exceeding a selected temperature. If thetemperature exceeds the selected temperature, the circuit canautomatically reduce power to the heating element 1750 until thetemperature returns to the selected level.

As discussed above, it is often desirable to warm patients while theyare undergoing x-ray exams. If the patients are situated on heating padsthat include temperature sensors and associated circuitry that are notradiolucent, however, this hardware may inhibit or otherwise preventobtaining usable x-ray images. To overcome this problem, patientpositioning/warming devices in accordance with the present invention caninclude a number of features to enhance radiolucency. As describedabove, such devices can include fiber optic cables, fiber optictemperature sensing devices, thermal chromatic state-changing switchdevices, nonmetallic heating elements, and/or other similar devices.

Various aspects of the positioning/warming device 1740 described abovecan be at least generally similar in structure and function to one ormore of the heating pads and/or heating mattresses described in detailin pending patent application Ser. No. 09/880,725 or in pendingprovisional application No. 60/374,853. In addition, the variousembodiments of the invention described herein can be modified andcombined with aspects of the embodiments disclosed in these pendingapplications to provide different embodiments than those disclosedherein. Further, FIGS. 17A-D describe only one embodiment of a patientpositioning/warming device in accordance with the present invention. Inother embodiments, such devices can include other features withoutdeparting from the present disclosure. For example, in very generalterms, patient positioning/warming devices in accordance with thepresent invention can include a shaped pressure relief portion (e.g., afoam portion) configured to support part of a patient during a medicalprocedure and a heating element portion configured to provide warmth tothe patient during the medical procedure. Accordingly, the presentinvention is not limited to the particular embodiments described herein.

For example, in another embodiment, a device configured in accordancewith the present invention can include a plurality of loose foam pieces(e.g., foam pieces such as those typically found in “bean bag chairs”)contained within a cover. One advantage of using loose foam piecesrather than a shaped piece of foam may be that the device is more easilyconformable to a particular position or a particular shape of thepatient. In yet other embodiments, it is expected that somepositioning/warming devices in accordance with the present invention maynot include any foam but instead may utilize a rigid or quasi-rigidmaterial that suitably conducts heat to the patient while comfortablypositioning the patient. It is further expected that yet otherembodiments may utilize fibrous materials in place of foam. Such fibrousmaterials may include both natural and manufactured fibers or fillmaterial. For example, in one embodiment, such fibrous materials mayinclude nylon fibers and/or wool fibers. In still further embodiments,it is expected that at least portions of heating pads and patientpositioning/warming devices configured in accordance with the presentinvention can include air-filled compartments. Such compartments can beused as pressure relief or shaping features of the heating devices.

As mentioned above, a wide variety of shapes and sizes of patientpositioning/warming devices are possible in accordance with the presentinvention. A few of such devices are illustrated in FIGS. 18A-C. FIG.18A, for example, is an isometric view of a patient warming system thatincludes two armboards 1840 configured in accordance with an embodimentof the invention. Each of the armboards 1840 includes a concavecontoured portion 1852 configured to receive and accommodate a patient'sarm. In one aspect of this embodiment, the basic construction of thearmboards 1840 can be at least generally similar to the construction ofthe positioning/warming device 1740 described above with reference toFIGS. 17A-D. As shown in FIG. 18A, the armboards 1840 can be positionedproximate to the heating pad 110 in such a way as to provide warmth to apatient's arms when they are extended at least partially outwardly fromthe patient's body. In one embodiment, each of the armboards 1840 canreceive an independent power line from an associated control unit. Inanother embodiment, a junction can be used to split a single power linebetween both of the armboards 1840.

FIG. 18B is an isometric view of a patient warming system that includesa roll 1856 configured in accordance with another embodiment of theinvention. The roll 1856 of the illustrated embodiment has a flatportion 1857 for stability and a generally cylindrical portion 1858. Theroll 1856 can be used to elevate and warm the patient's knees, head,feet or other appendages as desired to facilitate a particular medicalprocedure or to induce a particular therapeutic effect.

FIG. 18C is an end elevation view of a patient positioning/warmingdevice 1858 configured in accordance with yet another embodiment of theinvention. In one aspect of this embodiment, the positioning/warmingdevice 1858 includes a contoured recessed portion 1842 configured toprovide warmth to a patient P while positioning the patient P on his/herside. As will be apparent to those of ordinary skill in the relevant artbased on the embodiments of the invention described above, many otherconfigurations of patient positioning/warming devices are possible inaccordance with the present invention in addition to those describedabove.

FIG. 19 is a partially schematic, isometric view of a patient warmingsystem 1900 including one or more patient warming blankets 1960configured in accordance with another embodiment of the invention. Inone aspect of this embodiment, the patient warming blankets 1960 caneach include a heating element 1950 attached to an accessory controlunit 1922 via power lines 1934 a, b. The heating element 1950 may be atleast partially enclosed in foam to provide the patient warming blankets1960 with desirable heat retention and/or compression characteristics.Accordingly, in the illustrated embodiment, the patient warming blankets1960 may be at least generally similar in construction to one or more ofthe heating devices described above with reference to FIGS. 1-18. Onedifference, however, may be that the patient warming blankets 1960include much less foam such that they behave like typical blankets wouldwhen laid over a patient P or over a portion of the patient's body. Forexample, in another aspect of this embodiment, the patient warmingblankets 1960 can be wrapped around an appendage of the patient P, suchas the patient's arm or leg, to provide sufficient warming to theappendage during a particular medical procedure. In other embodiments,the patient warming blankets 1960 can simply be draped over a portion ofthe patient's body to provide desired warmth. In still furtherembodiments, the heating blankets 1960 can include one or moreattachment features to hold the heating blankets snugly in place on thepatient for improved heat retention. Such attachment features caninclude buckles, snaps, ties, adhesive tape, Velcro®, or other similardevices.

FIG. 20 is a partially schematic, isometric view of a patient warmingsystem 2000 configured in accordance with yet another embodiment of theinvention. In one aspect of this embodiment, the patient warming system2000 can be used by a medical practitioner to position and warm a femalepatient (not shown) undergoing various gynecological procedures. In theillustrated embodiment, for example, the patient warming system 2000includes stirrup warming devices 2070 a and 2070 b. The stirrup devices2070 may be employed in a typical stirrup configuration known to thoseof skill in the art. In a further aspect of this embodiment, however,the stirrups 2070 can include contoured positioning/warming devicessimilar to those described above to provide warmth to the patient's legsand feet during the procedure. Such warmth may provide patient comfortand possibly reduce the likelihood of undesirable temperature-relatedside effects of the procedure.

FIG. 21 illustrates a flow diagram of a routine 2100 for controlling thetemperature of a heating pad in accordance with an embodiment of theinvention. The routine 2100 starts when an operator or practitionerselects a temperature for the heating pad with a corresponding controlunit. In one embodiment, the operator can select this temperature bydepressing the appropriate button on the control unit (e.g., the controlunit 120 of FIG. 1). For ease of reference, the selected temperaturewill be referred to here as T_(sel). In block 2102, the control unitprovides power to the heating element in response to the operator'sselection of a temperature. In decision block 2104, the routinedetermines if the temperature of the heating pad is greater than theselected temperature T_(sel). (Or, alternatively, the routine can set amargin above the selected temperature, for example, 3° F., and determineif the temperature of the heating pad is greater than the selectedtemperature plus the margin.) If the temperature of the heating pad isgreater than the selected temperature T_(sel), then in block 2106 theroutine starts a clock at time=Ti₀, and in block 2108, the control unitcuts off power to the heating element. In decision block 2110, theroutine again checks the pad temperature to determine if it stillexceeds the selected temperature. If the pad temperature no longerexceeds the selected temperature, then the routine returns to block 2102and the control unit again provides power to the heating element tomaintain the pad temperature at or near the selected temperature.

Referring to decision block 2110, if the pad temperature continues toexceed the selected temperature, then the routine proceeds to decisionblock 2112 to determine if the elapsed time Ti is greater than or equalto a preset time interval X_(min). In one embodiment, the preset timeinterval X_(min) can be about 10 minutes. In other embodiments, othertime intervals can be chosen depending on various factors that maydiffer depending on the particular application. For example, in oneother embodiment, the preset time interval X_(min) can be about 5minutes. If in decision block 2112 the elapsed time Ti is not equal toor greater than the preset time interval X_(min), then the routinereturns to decision block 2110 to again check the temperature of theheating pad. If the heating pad temperature still exceeds the selectedtemperature T_(sel), then the routine again returns to decision block2112 to determine if the elapsed time Ti is equal to or greater than thepreset time interval X_(min). If the elapsed time Ti is now equal to orgreater than the preset time interval X_(min), then in block 2114, theroutine activates an alarm. As described above, this alarm can include avisible alarm, such as a flashing light, or an audible alarm. The alarmcan notify the operator that the heating pad has exceeded the selectedtemperature for the preset time interval X_(min). In this situation, theoperator may elect to remove the patient from the heating pad and/orinvestigate to see if the reason for the high temperature is readilyapparent.

Returning to decision block 2104, if the heating pad temperature doesnot exceed the selected temperature T_(sel), then the routine proceedsto decision block 2116 to determine if the operator has selected a newheating pad temperature. If the operator has selected a new temperature,then the routine returns to decision block 2104 to determine if theheating pad temperature exceeds the newly selected temperature T_(sel).If the heating pad temperature does exceed the newly selectedtemperature, then the routine proceeds as described above to reduce theheating pad temperature by cutting power to the heating element.

Returning to decision block 2116, if the operator has not selected a newheating pad temperature, then the routine proceeds to decision block2118 to determine if the operator has switched the heating pad off. Ifthe operator has switched the heating pad off, then power to the heatingelement is cut and the routine is complete. If the operator has notswitched the heating pad off, then the routine returns to block 2102 andthe control unit continues to provide power to the heating element. Fromhere, the routine proceeds as described above to ensure that either 1)the heating pad temperature does not exceed the selected temperatureT_(sel) for the preset time interval X_(min), or 2) if the heating padtemperature does exceed the selected temperature T_(sel) for the presettime interval X_(min), the alarm will activate.

One advantage of the embodiment of the invention described above withreference to FIG. 21 is that the alarm will not activate until theheating pad temperature has exceeded the selected temperature for apredetermined period of time. Thus, the alarm will not activateinadvertently due to a momentary spike in temperature. For example, incertain medical procedures, the use of a cauterizing device (e.g., acauterizing pencil or a device known in the medical field as a “rollerball”) can cause some temperature sensors in the proximity of thecauterizing device to register a momentary temperature spike. Thismomentary temperature spike does not reflect the actual temperature ofthe heating pad on which the patient may be lying. As will beappreciated by those who conduct such procedures, it would beundesirable to have the alarm activated every time one or more of thetemperature sensing devices responded to an erroneous signal from thecauterizing device. The delayed alarm activation routine as describedherein controls the alarm so that it will only be activated when theheating pad exceeds the selected temperature for a preset period oftime. As a result, such momentary temperature spikes will not result anerroneous alarm activation.

FIG. 22 is an enlarged rear isometric view of the heating pad controlunit 1021 of FIG. 10 illustrating an attachment device 2210 configuredin accordance with an embodiment of the invention. In one aspect of thisembodiment, the attachment device 2210 can include a base portion 2212and a clamp portion 2214. The base portion 2212 can be releasablyattached to the control unit 1021 by, for example, two hooks 2216extendable outwardly from the control unit 1021. The clamp portion 2214can include a first v-block 2217 a operably connected to a rotatableadjustment knob 2218, and a stationary second v-block 2217 b. In anotheraspect of this embodiment, the control unit 1021 can be releasablyattached to the IV pole 1002 by rotating the adjustment knob 2218 toclamp the IV pole 1002 between the first v-block 2217 a and the secondv-block 2217 b.

As will be appreciated by those of ordinary skill in the relevant art,the attachment device 2210 described above with reference to FIG. 22illustrates but one possible attachment device that can be used toreleasably attach the control unit 1021 to a typical OR structure, suchas the IV pole 1002. Accordingly, in other embodiments, the control unit1021 can be releasably attached to IV poles and other structures usingother attachment devices. For example, in one embodiment, the controlunit 1021 can include hooks that allow it to be releasably suspendedfrom the edge of an OR table.

FIG. 23 is a partially cutaway, top isometric view of a heating pad 2310configured in accordance with a further embodiment of the invention.Many aspects of the heating pad 2310 can be at least generally similarin structure and function to corresponding aspects of the heating pad1310 described above with reference to FIG. 13, or the heating pad 1210described above with reference to FIG. 12. For example, in one aspect ofthis embodiment, the heating pad 2310 includes a heating element 2350positioned at least generally between a first support portion 2340 and asecond support portion 2342. In one embodiment, the first and secondsupport portions 2340, 2342 can include compressible materials, such aspressure-relief foam materials, configured to provide distributedsupport for a person positioned on the heating pad 2310. In otherembodiments, the first support portion 2340 and the second supportportion 2342 can include other materials. Alternatively, in anotherembodiment, one or both of the support portions 2340, 2342 may beomitted.

In a further aspect of this embodiment, the heating pad 2310 includes acover 2312 enclosing the first support portion 2340 and the secondsupport portion 2342. In one embodiment, the cover 2312 can include anantimicrobial and abrasion-resistant fabric. In another embodiment, thecover 2312 can include an inner foam layer, such as a thin neoprene foamlayer, bonded to an outer membrane, such as a polyurethane membrane. Inaddition, in this embodiment the cover 2312 can further include a fabricsubstrate bonded to the foam layer toward the inside of the cover 2312.In other embodiments, the cover 2312 can include other materialsarranged in other configurations.

In another aspect of this embodiment, the heating element 2350 includesa plurality of conductive paths 2354 extending across a flexiblesubstrate 2351. The conductive paths 2354 can extend between a first busbar or first conductive lead 2353 positioned along a first edge 2357 ofthe flexible substrate 2351, and a second bus bar or second conductivelead 2355 positioned along a second edge 2359. The conductive paths 2354can be configured to generate heat by conducting electricity when thefirst lead 2353 is biased at a first electrical potential and the secondlead 2355 is biased at a second electrical potential. As described ingreater detail below, in one embodiment, the conductive paths 2354 candescribe non-linear paths across the flexible substrate 2351. The termnon-linear, as used herein, refers to a path that is substantially notstraight. Conversely, the term linear, as used herein, refers to a paththat is straight or at least generally straight.

One feature of aspects of the embodiment illustrated in FIG. 23 is thatflexible substrate 2351 and the conductive paths 2354 combine to makethe heating element 2350 relatively flexible. One advantage of thisfeature is that it allows the heating element 2350 to be positionedrelatively close to an upper surface 2311 of the heating pad 2310without destroying the favorable compression characteristics offered bythe first and second support portions 2340, 2342. For example, in oneembodiment, the first support portion 2340 can have a thickness T ofabout 1.5 inches or less. In another embodiment, the thickness T can beabout 1.0 inch or less. In a further embodiment, the thickness T can beabout 0.50 inch or less, such as 0.38 inch. In still other embodiments,the thickness T can have other values or, alternatively, the firstsupport portion 2340 can be omitted. Positioning the heating element2350 relatively close to the upper surface of the heating pad 2310 isadvantageous because more of the heat from the heating element 2350 goesto the patient, and less is dissipated passing through the first supportportion 2340.

Another feature of aspects of the embodiment illustrated in FIG. 23 isthat the conductive paths 2354 are relatively long, as compared toconductive paths extending between the first lead 2353 and the secondlead 2355 in generally straight lines. One advantage of this feature isthat increasing the length of the conductive paths 2354 increases theresistance. By increasing the resistance, the current draw required tomaintain the heating element 2350 at a given temperature can be reduced.

FIGS. 24A-24D are enlarged top views of portions of heating elements2450 (identified individually as heating elements 2450 a-d) illustratingvarious conductive path configurations in accordance with embodiments ofthe invention. Referring first to FIG. 24A, in one aspect of thisembodiment, the heating element 2450 a includes a plurality ofconductive paths 2454 a that describe repeating geometric patternsextending across at least a portion of a flexible substrate 2451 a. Inthe embodiment illustrated in FIG. 24A, the conductive paths 2454 adescribe a repeating “Greek key” pattern in which each Greek key 2455 ahas a height H and a width W. In one embodiment, the height H can beequal to about 1.0 inch and the width W can be equal to about 1.2inches. In other embodiments, the Greek key 2455 a can have otherdimensions. For example, in one other embodiment, the Greek key 2455 acan have a height H of more than about 1.0 inch, and/or a width W ofmore than about 1.2 inches. In yet another embodiment, the Greek key2455 a can have a height H of less than about 1.0 inch, and/or a width Wof less than about 1.2 inches. As described in greater detail below, inother embodiments the conductive paths 2454 a can describe otherpatterns.

Referring next to FIG. 24B, in one aspect of this embodiment, theheating element 2450 b includes a plurality of the non-linear conductivepaths 2454 a described above with reference to FIG. 24A, and a pluralityof at least generally linear conductive paths 2454 b, extending acrossat least a portion of a flexible substrate 2451 b. Both the non-linearconductive paths 2454 a and the linear conductive paths 2454 b can beconfigured to generate heat by conducting electricity between opposingbus bars or conductive leads (not shown in FIG. 24B). In the illustratedembodiment, the non-linear conductive paths 2454 a cross or intersectthe linear conductive paths 2454 b at various locations.

One feature of aspects of the invention described above with referenceto FIG. 24B is that the non-linear conductive paths 2454 a intersect thelinear conductive paths 2454 b in various places. One advantage of thisfeature is that if one of the linear conductive paths 2454 b happens tobreak in service, then one of the non-linear conductive paths 2454 awill reconnect the two portions of the broken non-linear conductive path2454 b together. As a result, heat output from the heating element 2450b will not be reduced if one or more of the linear conductive paths 2454b is broken during use. In this manner, the combination of thenon-linear conductive paths 2454 a and the linear conductive paths 2454b can provide the heating element 2450 b with a “self-healing” feature.

The non-linear conductive paths 2454 a illustrated in FIGS. 24A, Brepresent one non-linear pattern (i.e., a Greek key pattern) that can beused in accordance with the present invention. Similarly, thearrangement of the linear conductive paths 2454 b illustrated in FIG.24B represents one such arrangement that can be used in accordance withthe present invention. Accordingly, in other embodiments, other linearand non-linear conductive path patterns, as well as other combinationsand arrangements thereof, can be used to generate heat without departingfrom the spirit or scope of the present disclosure.

FIGS. 24C, D are enlarged top views of portions of the heating elements2450 c, d, respectively, configured in accordance with other embodimentsof the invention. As shown in FIG. 24C, the heating element 2450 cincludes a plurality of non-linear conductive paths 2454 c extendingacross at least a portion of a flexible substrate 2451 c in a repeatinggeometric pattern. In the embodiment illustrated in FIG. 24C, thegeometric pattern resembles a square wave. Referring next to FIG. 24D,the heating element 2450 d includes a plurality of non-linear conductivepaths 2454 d extending across at least a portion of a flexible substrate2451 d in a repeating pattern resembling a sine wave. With either of thepatterns illustrated in FIGS. 24C, D, the heating elements 2450 c, d canfurther include one or more at least generally linear conductive pathsintersecting the non-linear conductive paths 2454 c, d. For example, inone embodiment, the heating elements 2450 c, d can further include anarrangement of linear conductive paths at least generally similar to thelinear conductive paths 2454 b described above with reference to FIG.24B.

As the reader will appreciate, the various non-linear patterns describedabove with reference to FIGS. 24A-24D are merely representative of someof the patterns possible in accordance with the present invention, andare by no means exhaustive. Accordingly, the present invention is notlimited to these particular embodiments. In addition, the presentinvention is not limited to conductive paths that describe non-linearpatterns. Specifically, in other embodiments, a heating elementconfigured in accordance with the present invention can includeexclusively linear conductive paths. For example, in one suchembodiment, a heating element can include conductive strands that extendacross a flexible substrate in a linear, or at least generally lineararrangement.

FIG. 25 is an enlarged isometric view taken from FIG. 23 of a portion ofthe heating element 2350 configured in accordance with an embodiment ofthe invention. In one aspect of this embodiment, the flexible substrate2351 can include a cloth or fabric material 2559, such as a nylon orpolyester material. Such materials may be knitted and/or woven, such asa fiber weave. In other embodiments, the flexible substrate 2351 caninclude other materials, including other natural and/or syntheticmaterials, in fabric, cloth, or sheet form. In further embodiments, itis expected that still other materials may be suitable for the flexiblesubstrate 2351.

In another aspect of this embodiment, the conductive paths 2354 caninclude one or more conductive yarns 2556 woven into the fabric material2559 (for example, as a textile knit) to produce the patterns describedabove with reference to FIGS. 24A, B. The present invention, however, isnot limited to the particular patterns described above in FIGS. 24A-D.In addition to the non-linear patterns illustrated, in anotherembodiment, the conductive yarns 2556 can be woven into the fabricmaterial 2359 to define linear, or at least generally linear, patternsthat extend across the flexible substrate 2351 in the absence ofnon-linear patterns. In one embodiment, the conductive yarns 2556 can bewoven into the fabric material 2359 by a Jacquard loom as the loomweaves the flexible substrate 2351 in a weave direction WD. GreenTextile Associates, Inc., of 190 Bellew Carver Road, Spartanburg, S.C.,29301, is one provider of such weaving capability. In other embodiments,other fabrication techniques using other suitable materials can be usedto produce a flexible substrate having non-linear and/or linearconductive paths configured in accordance with the present invention.

For example, in one other embodiment, the conductive paths 2354 caninclude conductive ink applied in a non-linear and/or a linear pattern.Such conductive ink may include carbon or silver oxide, among othermaterials. In further embodiments, conductive paths can be fabricatedusing conductive film or foil materials. In these other embodiments, theflexible substrate 2351 can include other materials different from or inaddition to the fabric material 2559. For example, the flexiblesubstrate 2351 can include a generally non-woven material, such as aplastic, vinyl, rubber, or kevlar® material, as well as other sheetmaterials.

FIG. 26 is an enlarged side view of the conductive yarn 2556 configuredin accordance with an embodiment of the invention. In one aspect of thisembodiment, the conductive yarn 2556 includes a plurality of conductivestrands 2662 wrapped around a nonconductive strand 2660. In oneembodiment, the nonconductive strand 2660 can include polyester. Forexample, the nonconductive strand 2660 can include a 150 denierpolyester strand from the Saunders Thread Company of 1010 E. Ozark Ave,Gastonia, N.C., 28054-0020. In other embodiments, the nonconductivestrand 2660 can include other materials having other weights, such asnylon materials. In further embodiments, the nonconductive strand 2660can be omitted from the conductive yarn 2556.

FIG. 27 illustrates an enlarged isometric cross-sectional view of one ofthe conductive strands 2662 configured in accordance with one embodimentof the invention. In one aspect of this embodiment, the conductivestrand 2662 includes a core portion 2764 and a conductive portion 2766carried by the core portion 2764. In one embodiment, the core portion2764 can include a non-conductive material. For example, the coreportion 2764 can include a 33 denier nylon strand. In anotherembodiment, the core portion can include a 20 denier nylon strand. Inother embodiments, other suitable materials can be used for the coreportion 2764, or alternatively, the core portion 2764 can be omitted.

In another aspect of this embodiment, the conductive portion 2766 caninclude a metallic plating. For example, in one embodiment, theconductive portion 2766 can include silver plating. Silver includesanti-bacterial properties that may provide certain benefits in medicalapplications, such as limiting colonization of infectious matter. In oneaspect of this embodiment, the silver plating can have a thickness ofabout 100 microns or less. In another embodiment, the silver plating canhave a thickness of about 75 microns or less. In a further embodiment,the silver plating can have a thickness of about 50 microns or less. Inyet another embodiment, the silver plating can have a thickness of about10 microns or less, such as about 5 microns or less. In still furtherembodiments, other suitable materials having other thickness can be usedfor the conductive portion 2766. Noble Fiber Technologies, of 421 SouthState Street, Clarks Summit, Pa. 18411 can provide silver plated nylonstrands for use in selected embodiments of the invention as describedabove.

Although the conductive portion 2766 as illustrated in FIG. 27 appearsto evenly coat the core portion 2764 in a continues fashion, thisdepiction is provided here solely for purposes of illustration.Accordingly, in other embodiments, the conductive portion 2766 can becarried by the non-conductive portion 2764 in other manners. Forexample, in one other embodiment, it is expected that the conductiveportion 2766 can be carried by the core portion 2764 in an uneven andsomewhat random fashion without departing from the spirit or scope ofthe present invention.

One feature of aspects of the invention described above with referenceto FIGS. 23-27, is that the average current draw and/or heat output ofthe heating element 2350 can be controlled by varying the conductivityof the conductive yarn 2556 of FIG. 26. For example, in one embodiment,the conductivity of the conductive yarn 2556 of can be reduced by 50% byremoving one of the conductive strands 2662. In another embodiment, theconductivity of the conductive yarn 2556 can be reduced by reducing thedenier of the conductive strands 2662, for example, from 33 denier to 20denier. Alternatively, the conductivity of the conductive yarn 2556 canalso be increased by increasing the number and/or the denier of theconductive strands 2662. Changing the conductivity of a conductiveelement changes the resistance of the element. As a result, the currentdraw and/or the heat output of the heating element 2350 can becontrolled by varying the conductivity of the conductive yarns 2556 asdescribed above.

Another feature of aspects of the invention described above withreference to FIGS. 23-27, is that the radiolucency (or transparency tox-rays, or at least general transparency to x-rays) of the heatingelement 2350 can be controlled by controlling the thickness of theconductive portion 2766 of the conductive strand 2662. For example, inone embodiment, the heating element 2350 can be at least generallyradiolucent in an x-ray field having a strength of about 100 Roentgensor less if the conductive portion 2766 includes silver plating having athickness of about 5 microns or less, such as about 3 microns. In otherembodiments, the radiolucency of the heating element 2350 can beprovided, or at least increased, by using other materials having otherthicknesses. One advantage of this feature is that the heating pad 2310(FIG. 23) can be used to warm a patient during an x-ray exam withoutupsetting or otherwise distorting the x-ray images of the patient. Asdiscussed above, there are a number of hospital procedures where suchx-ray capability may be advantageous.

Although the foregoing discussion describes various configurations ofthe conductive yarn 2556 of FIG. 26, in other embodiments, otherconfigurations can be used without departing from the spirit or scope ofthe present invention. For example, in one other embodiment, instead ofyarn per se, the conductive “yarn” 2556 can include non fibrousmaterials such as conductive wires or filaments. Thus, the invention isnot limited to the particular conductive elements described above, butextends to other such elements capable of generating heat by conductingelectricity.

FIG. 28 is a flow diagram of a routine 2800 for providing power to aheating element in accordance with an embodiment of the invention. Inblock 2802, the routine receives a temperature selection TS. In oneembodiment, the temperature selection TS can be received from anoperator of the heating pad who selects the temperature with anassociated control unit. In block 2804, in response to receiving thetemperature selection, the routine provides power to the heatingelement. In block 2806, the routine determines a heating elementtemperature TE. In decision block 2808, the heating element temperatureTE is compared to a first temperature T1 to determine if TE is equal toor greater than T1. In one embodiment, T1 can be selected to beincrementally higher than the heating element temperature TE. In thismanner, the heating element can be heated to a temperature higher thanthe desired surface temperature to compensate for any temperature lossesoccurring between the heating element and the surface of the heatingpad.

If the heating element temperature TE is not equal to or greater thanT1, then in decision block 2810, the routine determines if the heatingpad has been switched off by, for example, the heating pad operator. Ifthe heating pad has not been switched off, then the routine returns toblock 2804 and continues to provide power to the heating element. If,instead, the heating pad has been switched off, then the routine iscomplete.

Returning to decision block 2808, if the heating pad temperature TE isequal to or greater than T1, then the routine proceeds to decision block2812 to determine if the heating pad temperature TE is greater than asecond temperature T2. In one aspect of this embodiment, the secondtemperature T2 can be selected to be incrementally higher than the firsttemperature T1 to define a temperature band for the heating element fora given temperature selection TS. For example, in one embodiment, if theoperator selects a heating pad surface temperature of 39° C., then theroutine can set the heating element temperature TE at 41° C. tocompensate for any heat dissipation that occurs between the heatingelement and the surface of the heating pad. To maintain the heatingelement temperature within an acceptable band, the second temperature T2can be set at 43° C. In this manner, the heating element can becontrolled within a temperature band that is incrementally higher thanthe desired surface temperature of the heating pad.

Returning to decision block 2812, if the heating element temperature TEis greater than the upper temperature limit T2, then the routineproceeds to block 2814 and cuts power to the heating element. Theroutine then proceeds to block 2806 to again determine the heatingelement temperature TE and this portion of the routine repeats. If theheating element temperature TE is not greater than the upper temperaturethreshold T2, then the routine proceeds to decision block 2816 todetermine if the heating pad has been switched off. If the heating padhas been switched off, then the routine is complete. If the heating padhas not been switched off, then the routine returns to block 2806 toagain determine the heating element temperature TE.

The routine 2800 described above with reference to FIG. 28 can be usedto warm the surface of a heating pad to a selected temperature whilecompensating for heat losses within the heating pad. For example, in oneembodiment, assume the heating pad operator selects a heating padtemperature of 39° C. In this embodiment, the routine can control theheating element temperature TE between a temperature band of 41° C. and43° C. In this manner, the heating element will at an incrementallyhigher temperature than the surface of the heating pad to compensate forany heat losses within the pad.

FIG. 29A is a partially cut away top view of a heating sheet 2910configured in accordance with an embodiment of the invention. FIG. 29Bis an exploded side cross-sectional view of the heating sheet 2910 ofFIG. 29A, taken substantially along line 29B-29B in FIG. 29A. Referringto FIGS. 29A and 29B together, in one aspect of this embodiment, theheating sheet 2910 includes a heating element 2950 positioned between afirst fill layer 2940 and a second fill layer 2942. In one embodiment,the first and second fill layers 2940, 2942 can include foam, such asviscoelastic foam having a thickness of about 0.5 inch or less. Inanother embodiment, the first and second fill layers 2940, 2942 caninclude foam having a thickness of about 0.25 inch or less.Additionally, the first and second fill layers 2940, 2942 can includematerials with anti-microbial properties to limit the colonization ofinfectious matter inside of the heating sheet 2910. In otherembodiments, the first and second fill layers 2940, 2942 can includeother suitable materials having other thicknesses. Alternatively, inselected embodiments, one or more of the first and second fill layers2940, 2942 can be omitted.

In another aspect of this embodiment, the heating element 2950 and thefirst and second fill layers 2940, 2942 can be enclosed in aform-fitting and fluid-resistant cover 2912. The outer seams of thecover 2912 can be sonically bonded or otherwise joined together toprovide a fluid-resistant barrier around the heating sheet 2910. In oneembodiment, the cover 2912 can be at least generally similar to thecover 112 described above with reference to FIG. 5, and/or the cover1212 described above with reference to FIG. 12. For example, in oneembodiment, the cover 2912 can include material that is impervious tofluids and does not react or breakdown with exposure to quantinary orother abrasive cleaning agents, including bleach. In other embodiments,the cover 2912 can include other fluid-resistant materials suitable foruse in hospital applications. Top portions of the cover 2912 and thefirst fill layer 2940 are cut away in FIG. 29A for purposes ofillustrating various aspects of the heating element 2950.

In a further aspect of this embodiment, the heating element 2950 can beat least generally similar in structure and function to the heatingelement 2350 described above with reference to FIG. 23. For example, theheating element 2950 can include a first bus bar or first conductivelead 2953, a second bus bar or second conductive lead 2955, and aplurality of conductive paths 2954 extending between the firstconductive lead 2953 and the second conductive lead 2955. As discussedabove with reference to FIGS. 23-25, in one embodiment, the conductivepaths 2954 can create non-linear patterns, such as a Greek key patterns.In other embodiments, the heating element 2950 can include other linearand non-linear conductive path configurations suitable for generatingheat by conducting electricity.

As shown in FIG. 29B, in yet another aspect of this embodiment, theheating element 2950 can be folded over on itself for increased heatoutput. In addition, a flexible backing layer 2970 can be bonded,laminated, and/or otherwise adhered to the heating element 2950 toprovide an insulative and/or support layer between the two foldedportions. In one embodiment, the backing layer 2970 can include apolylaminate material, such as polyurethane film having a thickness ofabout 0.0015 inch. In other embodiments, other suitable materials can beused to insulate and/or support portions of the heating element 2950.Alternatively, in other embodiments, such as embodiments in which theheating element is not folded, the backing layer 2970 can be omitted.

Referring to FIG. 29A, power lines 2931, 2932 pass from a utility cord2930 into the heating sheet 2910 via a sealed opening 2909 formed in thecover 2912. The first power line 2931 can be operatively connected tothe first lead 2953 and configured to bias the first lead 2953 at +24VDC. Similarly, the second power line 2932 can be operatively connectedto the second lead 2955 and configured to bias the second lead 2955 at−24 VDC. When the first and second leads 2953, 2955 are biased atdifferent electrical potentials, the heating element 2950 generates heatby conducting electricity through the conductive paths 2954.

In yet another aspect of this embodiment, the heating sheet 2910 canfurther include a number of devices configured to prevent the heatingsheet 2910 from exceeding a selected temperature. For example, in theillustrated embodiment, the heating sheet 2910 can include a pluralityof thermostats 2904 (individually identified as thermostats 2904 a-c)connected in series with the first power line 2931. In operation, thethermostats 2904 can be configured to activate if the temperature of theheating element 2950 exceeds a preselected over-temperature condition.For example, in one embodiment, the thermostats 2904 can be configuredto activate if the temperature of the heating element 2950 exceeds 49°C. If this temperature is exceeded, then one or more of the thermostats2904 can activate, thereby cutting power to the first lead 2953 andstopping the generation of heat. In one embodiment, the thermostats 2904can include snap-acting thermostats, such as those provided by the OtterCorporation. In other embodiments, the heating sheet 2910 can includeother devices to limit or otherwise control the temperature of theheating element 2950.

In a further aspect of this embodiment, the heating sheet 2910 caninclude at least one temperature sensor 2960 for measuring the operatingtemperature of the heating sheet 2910. A first instrumentation line 2933and a second instrumentation line 2934 can operatively connect thetemperature sensor 2960 to a control unit (not shown) via the utilitycord 2930. The temperature as measured by the temperature sensor 2960can be displayed by the control unit for viewing by a practitioner oroperator of the heating sheet 2910.

In addition, the temperature sensor 2960 can also be utilized in themanner described above with reference to FIG. 12 to control thetemperature of the heating sheet 2910. For example, in this embodiment,the temperature sensor 2960 measures the temperature proximate to thesurface of the heating sheet 2910, and communicates this information tothe control unit. If at any time the surface temperature as measured bythe temperature sensor 2960 exceeds the temperature selected by theoperator, the control unit can shut off power to the heating element2950. Once the temperature falls to at or near the selected temperature,the control unit can resume providing power to the heating element 2950to maintain the selected temperature. In one embodiment, the temperaturesensor 2960 can be a resistive thermal device (RTD), such as thoseprovided by the Minco Corporation. In other embodiments, the heatingsheet 2910 can include other temperature sensors in otherconfigurations.

The foregoing discussion of temperature sensors and/or temperaturecontrol devices is provided here solely for purposes of illustrating onemethod for controlling the temperature of the heating sheet 2910 inaccordance with the present invention. Accordingly, in otherembodiments, other temperature control monitoring devices, systems, andmethods can be used without departing from the spirit or scope of thepresent invention.

One feature of the embodiment described above with reference to FIGS.29A and 29B is that the heating sheet 2910 is at least generallyflexible. One advantage of this feature is that the heating sheet 2910can be draped over a portion of a person's body and conform to theperson's body to provide even warmth. Such features may be advantageousfor warming seated persons, such as a patient seated in a chair andundergoing a dialysis procedure. Due to the radiolucent aspects of theheating sheet 2910 described above, the heating sheet 2910 may alsooffer certain advantages by providing warmth to a patient undergoing anx-ray examination.

Another feature of the embodiment illustrated in FIGS. 29A and 29B isthe placement of the thermostats 2964 along opposing sides of theheating element 2950, and the placement of the temperature sensor 2960in a center portion of the heating element 2950. One advantage of thisfeature is that the thermostats 2964 and the temperature sensor 2960 canaccurately control the temperature of the heating sheet 2910 even whenit is draped over a patient and/or folded over on itself. The presentinvention, however, is not limited to the particularthermostat/temperature sensor arrangement illustrated in FIGS. 29A and29B.

In other embodiments, the heating sheet 2910 can include one or moremagnets 2980 for retaining surgical tools and/or other instruments in asterile field during an operation or other procedure. For example, inone embodiment, the magnets 2980 can be positioned beneath the cover2910 near the center portion of the heating sheet 2910. The magnets 2980may be secured to the cover 2912 by bonding or otherwise, or they may besecured to a portion of the first fill layer 2940. The magnets 2980 canbe shaped and sized so that a surgeon or other practitioner can placehis or her instruments near the magnets 2980 during an operation, andthe instruments will remain there until needed by the practitioner. In asimilar embodiment, the heating sheet 2910 can include one or morepockets (not shown) or other attachment features for temporary retentionof instruments and other devices.

FIG. 30A is a partially exploded side view of a pan-down assembly 3009configured in accordance with an embodiment of the invention forintroducing the utility cord 1430 into a heating pad 3010. FIG. 30B is abottom view of the pan-down assembly 3009 of FIG. 30A. Referring toFIGS. 30A and 30B together, in one aspect of this embodiment, thepan-down assembly 3009 includes a first recessed portion 3021 and asecond recessed portion 3022. The first recessed portion 3021 may be atleast generally similar to the pan-down 410 (FIG. 5), the pan-down 1209(FIG. 12), or the pan-down 1309 (FIGS. 13 and 14). As with the foregoingpan-downs, a connector 3004 sealably attaches the utility cord 1430within the first recessed portion 3021.

In another aspect of this embodiment, the second recessed portion 3022of the pan-down assembly 3009 can be configured to house the electronicmodule 1387 first discussed above with reference to FIG. 13. Asdescribed above with reference to FIG. 14, the power lines 1441-1444 canextend from the utility cord 3030 to the electronic module 1387. Thepower lines 1441 and 1442 can provide operating power to the electronicmodule 1387, and the power lines 1443 and 1444 can provide power toheating element leads (not shown) via the power lines 1331 and 1332. Asalso described above with reference to FIG. 14, the radiolucent cable1385 can bypass the electronic module 1387 and extend to a firsttemperature sensing device (not shown), and the fiber optic tubes 1388a, b can extend from the electronic module 1387 to a second temperaturesensing device (also not shown). The temperature sensing devices cancontrol the temperature of the heating pad 3010.

In a further aspect of this embodiment, the electronic module 1387 caninclude one or more lights 3082 that can illuminate to indicate variousmodes of operation of the electronic module 1387. For example, in oneembodiment, one or more of the lights 3082 can illuminate to indicatethat power is being provided to a heating element via the electronicmodule 1387. In another embodiment, one or more of the lights 3082 canilluminate to indicate that a temperature sensing device operativelycoupled to the electronic module 1387 is functioning properly.

In yet another aspect of this embodiment, the pan-down assembly 3009includes a removable access cover 3024 configured to be releasablyattached to the second recessed portion 3022 to secure the electronicmodule 1387 in place. In one embodiment, the access cover 3024 can be atleast generally transparent so that the lights 3082 on the electronicmodule 1387 are visible through the access cover 3024. One advantage ofthis feature is that an operator of the heating pad 3010 can confirm ata glance whether the heating element and/or fiber optic temperaturesensing devices are functioning properly by simply looking at the lights3082 through the transparent cover 3024.

One skilled in the relevant art will appreciate that embodiments of theinvention can be used in various environments other than the medicalapplications described above. For example, in one other environment,aspects of the invention can be utilized in a home setting to providepersonal warmth while sleeping in a particular position. For example, ifa person needs to sleep in a particular position for recuperation from amedical procedure, or for other reasons, one or more of the devicesdescribed above can be used to maintain such a position while providingsufficient warmth to the person. Further, it is expected that variousembodiments of the invention described above can be used in pediatricsettings for newborn and young children to provide warmth during sleep.In yet other applications, it is expected that various embodiments ofthe devices described above can be utilized during transport of personsin need of medical aid. Such transport may include, for example,ambulance transport in civilian and military settings.

Unless the context clearly requires otherwise, throughout the foregoingdescription and the following example, the words “comprise,”“comprising,” and the like are to be construed in an inclusive sense asopposed to an exclusive or exhaustive sense; that is to say, in thesense of “including, but not limited to.” Words using the singular orplural number also include the plural or singular number, respectively.Additionally, the words “herein,” “above,” “below” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application.

The foregoing description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. While specific embodiments of, and examples for, theinventions are described herein for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whilevarious embodiments of patient positioning/warming devices are describedabove utilizing one or more types of foam adjacent to a heating element,in other embodiments, other materials in addition to, or in place of,foam can be used to sandwich or otherwise enclose the heating element.Further, while specific types of heating elements are described abovefor purposes of illustration, in other embodiments, it is expected thatvarious other types of heating elements can be used.

All of the patent applications cited herein are incorporated byreference in their entireties. Accordingly, aspects of the inventiondisclosed herein can be modified, if necessary, to employ or incorporatethe systems, functions and concepts of the cited patent applications toprovide yet further embodiments of the inventions. These and otherchanges can be made to the invention in light of the detaileddescription.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustrationbut that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A heating element comprising: a flexible substrate; and a pluralityof conductive strands supported by the flexible substrate, each of theconductive strands having: a core portion; and a conductive portioncarried by the core portion, wherein each of the conductive strands isconfigured to generate heat by conducting electricity.
 2. The heatingelement of claim 1 wherein the flexible substrate includes a fabricmaterial, and wherein the plurality conductive of strands are interwovenwith the fabric material.
 3. The heating element of claim 1 wherein theflexible substrate includes a nylon weave, and wherein the plurality ofconductive strands are interwoven with the nylon weave.
 4. The heatingelement of claim 1 wherein the flexible substrate includes a fabricmaterial, wherein each of the conductive strands includes anon-conductive core and metallic plating, and wherein the plurality ofconductive strands are interwoven with the fabric material.
 5. Theheating element of claim 1 wherein the flexible substrate includes anylon weave, wherein each of the conductive strands includes a nyloncore with a silver portion, and wherein the plurality of conductivestrands are interwoven with the nylon weave.
 6. The heating element ofclaim 1 wherein the core portion of each of the conductive strands is atleast generally non-conductive.
 7. The heating element of claim 1wherein the conductive portion of each of the conductive strandsincludes metal.
 8. The heating element of claim 1 wherein each of theconductive strands includes a nylon core with metallic plating.
 9. Theheating element of claim 1 wherein each of the conductive strandsincludes a nylon core with silver plating.
 10. The heating element ofclaim 1 wherein the conductive portion of each of the conductive strandsincludes silver having a thickness of about 100 microns or less.
 11. Theheating element of claim 1 wherein the conductive portion of each of theconductive strands includes silver having a thickness of about 10microns or less.
 12. The heating element of claim 1 wherein theconductive portion of each of the conductive strands includes silverhaving a thickness of about 5 microns or less.
 13. The heating elementof claim 1 wherein the plurality of conductive strands forms anon-linear pattern on the flexible substrate.
 14. The heating element ofclaim 1 wherein the plurality of conductive strands forms a repeatinggeometric pattern on the flexible substrate.
 15. The heating element ofclaim 1, further comprising a plurality of non-conductive strands,wherein each of the non-conductive strands is entwined with at least oneof the conductive strands to form a plurality of conductive yarnssupported by the flexible substrate.
 16. The heating element of claim 1,further comprising a plurality of non-conductive strands, wherein eachof the non-conductive strands is entwined with at least one of theconductive strands to form a plurality of conductive yarns, and whereinthe plurality of conductive yarns are woven into the flexible substrate.17. The heating element of claim 1, further comprising: a firstconductive lead supported by the flexible substrate, the firstconductive lead coupled to the plurality of conductive strands andconfigured to be biased at a first electrical potential; and a secondconductive lead supported by the flexible substrate and spaced apartfrom the first conductive lead, the second conductive lead coupled tothe plurality of conductive strands and configured to be biased at asecond electrical potential to cause electrical current to flow througheach of the conductive strands and generate heat.
 18. The heatingelement of claim 1 wherein the core portion of each of the conductivestrands includes nylon yarn of about 100 denier or less.
 19. The heatingelement of claim 1 wherein the core portion of each of the conductivestrands includes nylon yarn of about 33 denier or less.
 20. The heatingelement of claim 1, further comprising a plurality of polyester strands,wherein each of the polyester strands is entwined with at least one ofthe conductive strands to form a plurality of conductive yarns, whereinthe plurality of conductive yarns are interwoven with the flexiblesubstrate. 21-102. (canceled)